SGRT-based DIBH radiotherapy practice for right breast cancer combined with RNI: A retrospective study on dosimetry and treatment accuracy

SGRT-based DIBH radiotherapy practice for right breast cancer combined with RNI: A retrospective study on dosimetry and treatment accuracy | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article SGRT-based DIBH radiotherapy practice for right breast cancer combined with RNI: A retrospective study on dosimetry and treatment accuracy Jianjun Lai, Haili Hu, Lu Jiang, Jing Wu, Lan Lei, Chuanfeng Zhang, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-2185678/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Background: This paper studied retrospectively the dosimetry and therapeutic accuracy of deep inspiration breath hold (DIBH) radiotherapy in regional nodal radiation (RNI)-containing right-sided breast cancer patients who had completed treatment based on surface guided radiotherapy (SGRT) technology, hoping to clarify the clinical application value and related issues . Methods: Free breath (FB) and DIBH plans were prepared for31 RNI-containing right breast cancer patients who had completed DIBH radiotherapy based on SGRT technology. Four organs at risk (OARs) including heart, right coronary artery (RCA), right lung and liver were made dosimetriccomparison on the premise that the planning target volume was met dose-volume prescription requirements. Meanwhile, 31 patients were divided into edge of xiphoid process (EXP), sternum middle (SM)and left breast wall (LBW) groups according to different positions of respiratory gating primary points. The CBCT setup error data of the three groups were contrasted for the treatment accuracy study, and the effects of different gating window heights on the lung volume increment of the right side were compared among the three groups. Results: All planning target volume met the dose-volume coverage criteria. Compared with FB, DIBH slumpedthe maximum dose of heart and RCA by 44.3% and 46.7% respectively. The mean dose was went down by 12.5% for right lung. The mean liver dosedecreased the most, with an average reduction rate of 69.4%. The setup error of EXP group in the anterior-posterior (AP) direction was 3.6±4.5mm, significantly higher than the other two groups (2.2±2.6mm, 2.4±3.1mm). The rightlung volume increment in EXP, SM and LBW groups was 72.3%, 69.9 % and 67.2%, respectively(P=0.08), and the corresponding breath-holding heights were 13.5±3.7mm, 10.3±2.4mm, and 9.6±2.8mm, respectively(p<0.05). Conclusions: SGRT-based DIBH can better protect the heart, RCA, ipsilateral lung and liver of right breast cancer patients combined with RNI. Different respiratory gating primary points have different therapeutic accuracy and breath-hold height. On the premise of reasonable respiratory gating primary points, interfractions can be widely applied as it has high repeatability and breath-holding stability to ensure therapeutic accuracy. Right-sided breast cancer Radiotherapy DIBH SGRT Figures Figure 1 Figure 2 Figure 3 Background In recent years, breast cancer has become the most common malignant tumor in women worldwide 1 – 3 . Existing mainstream treatment mode for breast cancer is still a comprehensive treatment mode including surgery, chemotherapy, radiotherapy, targeted therapy and gene therapy 4 , 5 . Postoperative combined radiotherapy can reduce the local and distant recurrence rate, improve the local control rate and mend the prognosis for patients 6 , 7 . In radiotherapy for breast cancer, organs at risk (OARs) and normal tissues around the target region are typically irradiated to a certain extent. Especially for patients with regional nodal radiation (RNI), the larger irradiation region always inevitably expands the volume of normal tissues exposed to radiation while increasing therapeutic benefit, which in turn cranks up the risk of toxicity 7 , 8 . Deep inspiration breath hold (DIBH) can significantly ameliorate the risk of cardiotoxicity in patients with left breast radiotherapy, reduce the irradiation dose to the heart and its substructures amid left breast radiotherapy 9 , 10 , and benefit for the lung,liver and stomach to varying degrees 10 , 11 . Although DIBH is widely used in radiotherapy of left breast cancer, it is rarely used in radiotherapy for right breast cancer. Only a few scholars have performed dosimetric studies through the planning system.These studies show that DIBH can benefit for different patients in radiotherapy of right breast cancer to different degrees. In particular for patients with RNI, DIBH can significantly reduce the maximum dose of right coronary artery (RCA) and the volume of liver exposured at low dose 12 – 14 . The use of optical surface imaging technology in respiratory controlled radiotherapy can dynamically monitor the body surface position and respiratory movement data for patients in real time, which has the characteristics of non-radiation and high precision and is widely popular in DIBH gating radiotherapy for breast cancer 14 , 15 . Since May 2021, the department to which the author belongs had been using surface guided radiotherapy (SGRT) based DIBH radiotherapy for postoperative right breast cancer patients with RNI, and the author had been making retrospective study on the dosimetry and accuracy (repeatedly and stability) of SGRT-based DIBH radiotherapy pursuant to real treatment data, which aims to expound the clinical application value and related issues of this technique in RNI-containing radiotherapy for right breast cancer. Materials And Methods The inclusion criteria were patients who received RNI-containing right breast radiotherapy (after breast-conserving or radical surgery), had good compliance, and completed the entire DIBH treatment process. A total of 31 patients were screened, including 21 breast-conserving patients and 10 radical surgery patients, with an average age of 50.2 years (range:29–72 years). Figure 1 shows clinical treatment process of patients, including respiratory gating primary point setup, respiratory training, CT and optical surface image acquisition, treatment planning, setup and delivery, CBCT position verification and problem handling mechanism. lmmolilization, primary point setup and CT simulation For patients who were to receive DIBH radiotherapy for right breast cancer, individualized negative pressure vacuum bag molds were made for postures fixation and a laser-based surface scanner (Sentinel™, C-RAD AB, Sweden) was mounted on the localized CT end for respiratory gating operation. The respiratory gating primary point for breast-conserving patients were placed at the lower edge of the xiphoid process or the middle sternum. The gating primary point for radical surgery patients was set on the lateral wall of the left breast to avoid the bolus. Patients were trained to perform thoracic breathing, the width of the gating window at the primary point was 1.5-3mm, and it was reckoned that DIBH requirements were met when breath-holding duration was 20s and could be repeated for more than three consecutive times. 3mm CT images were acquired under FB and DIBH using a CT simulator (Somatom, Simenz, Germanny), reference images of the body surface under FB were acquired using Sentinel™ and sent to the accelerator end of optical-based surface scanner (Catalyst™, C-Rad AB,Sweden) together with the gating window parameters, and lung volume under FB and DIBH was delineated on CT images using an automatic segmentation tool. According to Oonsiri et al 47 reported and the previous DIBH practice experience for left breast cancer, the target volume of FB and DIBH should be delineated and planned simultaneously on the premise that the right lung volume under DIBH is greater than 50% of the right lung volume under FB. Target volume and organ at risks delineation, treatment and planning For the same patient, the same radiation oncologist delineated the OARs target volume on the CT images under FB and DIBH simultaneously. The gross tumor volume (GTV) and clinical target volume (CTV) were delineated according to the Radiation Therapy Oncology Group(RTOG) standard. PTV and PGTV were defined as the expansion of CTV and GTV by 10mm and the retraction to 5mm subcutaneously, respectively. The heart and liver were automatically generated by an automated segmentation tool and reviewed and manually adjusted by a radiation oncologist, and the RCA was manually delineated. The prescription dose of PTV was 5000cGy in 25 fractions in all patients, and PGTV was added to 5750cGy in 25 fractions for patients after breast conservation. The target volume dose-volume criteria were as recommended by ICRU as follows: Maximum dose of not exceeding 107%, coverage of PTV/PGTV by the 95% isodose. FB and DIBH radiotherapy plans were designed by the same radiotherapy physicist using 6MV-FFF ray energy for the same patient, and 4–7 tangential IMRT fields based on DMLC technology were used depending on the complexity of the plans. All patients underwent Monte Carlo dose calculation on the radiotherapy planning system (Monaco5.1, Elekta, Sweden). QUANTEC guidelines were used to limit and determine OARs dose-volume, and the dose and volume were kept as low as possible. Both FB and DIBH radiotherapy plans were reviewed and approved by the radiation oncologists. After confirming that the DIBH plan was overall superior to the FB plan,the DIBH radiotherapy plan was sent to the linear accelerator (LA) end (Infinity™,Elekta,Sweden) for plan verification and treatment. Setup and treatment implementation For the first treatment, after the laser line in the treatment room was aligned to the body surface marker line of patients under FB, the position was verified using an optical-based surface scanner (Catalyst™, C-RAD AB, Sweden) at the LA end. The verification criteria are the deviation of translation ≤ 3mm and the deviation of rotation ≤ 2°. Optical reference images were subsequently re-acquired under FB using Catalyst™ after position verification and calibration with CBCT under DIBH. In day-to-day treatment, both body surface marker and optical image positioning were performed according to the first treatment. CBCT was used to verify and calibrate the position under DIBH once a week and to re-collect FB optical reference images. In case of abnormal setup data in CBCT, the position re-verification by CBCT after adjusting position and breathing, which under DIBH mode was also checked before the treatment of the next day. All patients treatment with DIBH were triggered by the Response™ gating interface within a preset gating window for linear accelerator beam-on therapy. The Catalyst™ was used to monitor displacement in real time during treatment. Statistical analysis for dosimetric data and setup accuracy data Mann-Whitney U tests were used to analyse differences in the dose-volume constraints achieved of OARs between the FB and DIBH plans, which is suitable for data which are not normally distributed as confirmed by the Shapiro-Wilk test. Kruskal-Wallis H tests were used to analyse differences in multiple groups of sample data, which is also applicable to data which are not normally distributed as confirmed by the Shapiro-Wilk test. The statistical tests were conducted using SPSS27.0 and p < 0.05 was considered to be statistically significant. Results Dosimetric statistics for all DIBH and FB treatment plans In this study, FB and DIBH dosimetric data were collected from 31 right breast cancer patients having completed radiotherapy with DIBH. Coverage of PTV by 95% isodose and coverage of PGTV by 95%-100% isodose were set for both treatment plans. Table 1 summarizes the dose-volume data of four OARs under the premise that the dose-volume requirements of PTV and PGTV are met. Figure 2 shows the boxplot comparison of the dose-volume data of OARs in 31 patients. The indicators related to target volume dose-volume between the two groups of data met the requirements and there was no statistical difference, while the difference of all OARs dose-volume between the two groups of data was statistically significant. Table 1 Summary of treatment planning data for organs at risk, for the 31 right breast cancer patients included in this study, with deep inspiration breath-hold (DIBH)), free breath(FB) and 4–7 fields tangential IMRT (tlMRT). N = 31 FB DIBH 95%CI p Descent rate(%) Heart mean Dose(cGy) 225.2 ± 75.6 171.2 ± 48.9 31.2ཞ96.4 ༜0.05 25.2 Heart max Dose(cGy) 1666.9 ± 961.7 927.6 ± 390.5 366.6ཞ1112.1 ༜0.05 44.3 RAD mean Dose(cGy) 444.8 ± 161.6 342.4 ± 112.1 31.8ཞ173.2 ༜0.05 23.1 RAD max Dose(cGy) 1090.9 ± 569.5 581.1 ± 165.7 296.7ཞ722.6 ༜0.05 46.7 Lung-R mean Dose(cGy) 1332.1 ± 128.7 1165.4 ± 148.6 96.1ཞ237.3 ༜0.05 12.5 Lung-R V500cGy(%) 53.3 ± 3.0 48.3 ± 2.9 3.5ཞ6.5 ༜0.05 9.4 Lung-R V2000cGy(%) 25.7 ± 1.9 20.6 ± 3.2 3.8ཞ6.4 ༜0.05 19.2 Lung-R V3000cGy(%) 18.3 ± 2.5 15.3 ± 2.3 1.7ཞ4.1 ༜0.05 16.7 Liver mean Dose(cGy) 916.9 ± 318.9 281.2 ± 150.3 509.1ཞ762.4 ༜0.05 69.4 Dosimetric data are shown as mean values with one standard deviation for OARs. Mann-Whitney U tests were used for dosimetric data, and p < 0.05 was considered to be statistically significant. Most favourable value in deep inspiration breath hold was marked in bold. Descent rate(%) was the average decline for dose-volume data of four OARs after patients holds breath by deep inhalation. Cardiac dose Compared with FB plan, DIBH declined the mean dose of heart and RCA by 54.0 ± 16.7cGy and 22.4 ± 49.5cGy, respectively (P < 0.05), and the mean descent rates were 25.2% and 23.1%, respectively. The maximum dose of heart and RCA were decreased by 739.3 ± 571.2cGy and 509.8 ± 462cGy, respectively (P < 0.05), and the average reduction rates were 44.3% and 46.7%, respectively. This suggested that DIBH technology had a large dose decline value and decline rate for the maximum dose for heart and RCA and in terms of mean value, there was a significant difference (p < 0.05), but the dose decline value was slightly low because the mean dose to the heart was controlled at a low level in the two different breathing modes. Only 2 patients had a decrease in mean cardiac dose of over 100cGy (131.1cGy, 100.2cGy) and 3 patients shrank its RCA dose by more than 200cGy (249cGy, 289cGy, 328cGy). Pulmonary dose According to dose-volume data of right lung in this study, compared with FB technique, DIBH reduced right lung V500cGy, V2000cGy, V3000cGy and the mean dose of all patients to varying degrees. V500cGy decreased from 53.3 ± 3.0% to 48.3 ± 2.9%, V2000cGy went down from 25.7 ± 1.9% to 20.6 ± 3.2% and V3000cGy slumped from 18.3 ± 2.5% to 15.3 ± 2.3%. The mean dose contracted by 166.7 ± 19.9cGy. In FB mode, there were 9 patients whose V3000cGy exceeded 20%, which compared with 31 patients whose V3000cGy was controlled below 20% by DIBH technique. Liver The mean liver dose using FB technique was 916.9 ± 318.9cGy, and the mean liver dose exceeded l000cGy in 4 patients. After using DIBH technique, the mean liver dose was only 281.2 ± 150.3cGy, an average decrease of 69.4%. Of all 31 patients enrolled in this study, the mean liver dose of 3 patients decreased by more than l000cGy (1160cGy, l005cGy, 1149cGy), the mean liver dose of 4 patients was controlled below l00cGy (82cGy, 91cGy, 78cGy, 99cGy). This manifested that DIBH significantly decreased the mean liver dose for patients with RNI-containing right breast cancer. Comparison of position accuracy under different DIBH gating primary points The treatment accuracy study involved the setup error data calculated from 178 CBCT images in DIBH mode of 31 patients, including 78 in EXP group, 65 in SM group and 44 in LBW group. Table 2 shows the absolute value statistical results of three-dimensional setup errors under three different gating primary points placement conditions. When the DIBH gating primary points were placed on the edge of xiphoid process, sternum middle and contralateral breast wall, the corresponding overall positioning errors were 3.2 ± 4.0mm, 2.4 ± 3.0 m and 2.5 ± 3.2mm, respectively. It is obvious that the setup accuracy of gating primary point at EXP was worse than that of the other two groups. The setup error in AP direction was 3.6 ± 4.5mm at EXP, which was significantly higher than that of the other two groups (2.2 ± 2.6mm, 2.4 ± 3.1mm). In the SM group, the setup error interval of 0–3 mm accounted for up to 64.1%, and the setup error of 8mm only occurred in one fraction(CC direction). In the LBW group, the setup error interval of 0-3mm made up 59.8%, and also the set up error of 8mm only occurred in one fraction (RL direction). The set up error ranging 0 to 3mm accounted for 52.6% in EXP group, and up to 6 fractions (2.6%) had the errors over 8mm, of which 5 times appeared in the AP direction. DIBH radiotherapy has a good treatment accuracy overall, but the location of the gating point has a certain impact on the treatment accuracy. The stability and repeatability of the fractional treatment are relatively poor when the gating point is placed at the edge of xiphoid process. Table 2 Summary of setup error data for the 31 right breast cancer patients included in this study, with deep inspiration breath-hold (DIBH). Directions EXP(n = 11,f = 78) SM(n = 12,f = 65) LBW(n = 8,f = 44) p Setup error with any directions, mm All direction 3.2 ± 4.0 2.4 ± 3.0 2.5 ± 3.2 ༜0.05 AP direction 3.6 ± 4.5 2.2 ± 2.6 2.4 ± 3.1 ༜0.05 CC direction 3.3 ± 4.0 3.0 ± 3.7 2.8 ± 3.4 ༜0.05 RL direction 2.2 ± 2.8 2.3 ± 2.7 2.4 ± 3.0 = 0.13 Fractions with any excursion ∈[0, 3) mm, no. (%) All direction 123(52.6) 125(64.1) 79(59.8) ༜0.05 AP direction 30(12.8) 48(24.6) 23(17.4) ༜0.05 CC direction 32(13.7) 32(16.4) 26(19.7) ༜0.05 RL direction 59(25.2) 45(23.1) 30(22.7) ༜0.05 Fractions with any excursion ∈[3, 8) mm, no. (%) All direction 105(44.9) 69(35.4) 52(38.6) ༜0.05 AP direction 40(17.1) 17(8.7) 14(10.6) ༜0.05 CC direction 45(19.2) 32(16.4) 18(13.6) ༜0.05 RL direction 18(7.7) 20(10.3) 19(14.4) ༜0.05 Fractions with any excursion ∈[8,∞) mm, no. (%) All direction 6 (2.6) 1(0.5) 1(0.7) ༜0.05 AP direction 5(2.2) 0(0) 1(0.7) ༜0.05 CC direction 1(0.4) 1(0.5) 0(0) ༜0.05 RL direction 0(0) 0(0) 0(0) ༜0.05 Absolute value of setup error data from CBCT are demoted as mean values with one standard deviation. Setup error data were not normally distributed as confirmed by the Shapiro-Wilk test, so Kruskal-Wallis H tests were used to analyse differences in setup error data statistics, and p < 0.05 was considered to be statistically significant. Most favourable value in setup error is marked in bold. EXP, SM, and LBW represent the gating points placed on the edge of xiphoid process, sternum middle and left breast wall respectively. AP, CC and RL represent the anterior-posterior, cranio-caudal and right-left directions of the patients respectively. Lung volume increment and gating primary point height The right lung volume increment of 31 patients included in DIBH treatment process was ≥ 50%. In EXP group, the increment averaged 72.3%. The height of corresponding gating window was 13.5 ± 3.7 mm, with a height range of 9.2–20.l mm; In SM group, the average increase was 69.9%, the height of the gating window was 10.3 ± 2.4 mm, and the height range was 7.4-16.3mm. In the left breast wall group, the average increment was 67.2%. The height of the gating window was 9.6 ± 2.8mm, and the height range was 6.5-14.6mm. The height of the gating window is recorded as the average value of the upper and lower threshold. All the three groups have good lung volume increment through DIBH, but the height of the gating window was significantly different (p < 0.05). In sternum middle and contralateral breast wall groups, the height of the gating window was significantly lower, which compared with that in the EXP group. Table 3 Summary of height of gating window and corresponding right lung volume increment for the 31 right breast cancer patients included in this study, with deep inspiration breath-hold (DIBH). EXP(n = 11) SM(n = 12) LBW(n = 8) p Lung-R volume for FB (cm 3 ) 1230.9 ± 184.1 1177.3 ± 186.1 1208.9 ± 178.3 = 0.28 Lung-R volume for DIBH (cm 3 ) 2126.1 ± 237.2 1989.0 ± 294.6 2021.6 ± 312.5 = 0.36 Lung-R volume Increment rate (%) 72.3 69.9 67.2 = 0.08 Gating window Height (mm) 13.5 ± 3.7 10.3 ± 2.4 9.6 ± 2.8 ༜0.05 Lung-R volume and gating window height data are defined as mean values with one standard deviation. Volume and height data were not normally distributed as confirmed by the Shapiro-Wilk test, so Kruskal-Wallis H tests were used to analyse differences in volume and height data statistics, and p < 0.05 was considered to be statistically significant. Most favourable value in gating window height is marked in bold. EXP, SM, and LBW represent the gating points placed on edge of xiphoid process, sternum middle and left breast wall respectively. Discussion The toxicity risk of breast cancer radiotherapy has been widely concerned by radiation oncologists. Darvby et al 17 showed that the incidence of major coronary events after breast cancer radiotherapy was linearly increased with the mean cardiac dose. For every l00cGy increase in the mean dose to the heart, the corresponding probability of coronary adverse events hiked by 7.4%, and the risk of cardiotoxicity lasted for decades after treatment. Colossal amounts of studies have shown that amid left breast cancer radiotherapy, DIBH technology can separate the heart from mammary gland position, so as to significantly shrink the high dose volume and mean dose of the heart, and reduce heart disease risks associated 18 – 20 . Meanwhile, coupled with DIBH technology, it can also increase the lung volume, reduce the lung tissue density, which lowers the irradiation dose in the lung 13 , and slump the irradiation dose of the contralateral breast, stomach and liver to varying degrees 21 , 22 . Although DIBH technique is widely used in left-sided breast cancer, there are few reports on the clinical application of DIBH technique in right-sided breast cancer. According to several radiotherapy planning studies 23 – 27 , DIBH reduces lung dose compared with FB in patients with right-sided breast cancer and achieves liver protection during radiotherapy 25 . A radiotherapy planning study by Conway JL et al 13 showed that the mean lung dose was reduced by 340cGy and the mean cardiac dose was significantly slumped in patients undergoing DIBH irradiation coupled with internal mammary chain (IMC). A radiotherapy planning study conducted by Chloe et al 23 showed that 8 patients with RNI-containing right breast cancer were treated with DIBH technique. Their mean dose of the ipsilateral lung was decreased from 1820 ± 320cGy to 1590 ± 230 cGy, and maximum dose of RCA was reduced from 1160 ± 720cGy to 560 ± 290cGy. Although DIBH technology has obvious dosimetric value in right-sided breast radiotherapy, especially in the right breast with RNI irradiation, due to the complexity of the technology and the cost investment of time and labor, no large number of cases have been reported for clinical application. Abiding by 'as low as reasonably achievable'(ALARA) principle, DIBH radiation therapy for breast cancer patients with RNI had been conducted in our department since May 2021 and a retrospective study on dosimetry and accuracy for 31 breast cancer patients with RNI was conducted. In this study, the mean cardiac and RCA dose reduction rates by DIBH were 25.2% and 23.1%, respectively. However, the DIBH technique in left breast radiotherapy can reduce the mean dose of heart and LAD by 25–67% and 20–73%, respectively 28 , with an average reduction of 46% and 46.5%, respectively. In conclusion, in terms of the contribution of DIBH technology to the average decline rate for heart and RCA, the benefit of right breast cancer patients is significantly weaker than that of left breast cancer patients. It is speculated that, as the heart deviates from the right mammary gland, and the mean dose values of the heart and RCA are controlled at a low level under FB condition, although the distance between the heart and the chest wall is further increased by DIBH, its contribution to the mean reduction of the heart and its substructure is limited. With respect to maximum dose, DIBH technique significantly contracted the maximum dose of heart and RCA (decrease value: 740 ± 570cGy, 510 ± 460 cGy, P < 0.05), and the average decline rates were 44.3% and 46.7%, respectively. The results of this study were similar to those of Chloe et al 23 reported. A study by Altinok et al 29 showed that high doses of RCA in the heart, especially proximal part, increased the risk of coronary heart disease. During RNI irradiation, IMN is close to a small amount of heart volume, and DIBH technology can distance IMN from the heart, which significantly contributes to the reduction of the maximum dose of heart and RCA, and can reduce the risk of coronary heart disease in patients. Lung is an important OARs in breast cancer radiotherapy. In a meta-analysis of 742648 breast cancer patients, Grantzau and Overgaard 30 found that compared with patients who did not receive radiotherapy, patients accepted radiotherapy had a higher secondary lung cancer morbidity 5 and 15 years after treatment, 39% and 66% respectively. Due to advances in technology, the incidence of radiation pneumonitis (RP) after modern breast radiotherapy is lower (1%-5%) and pulmonary function decline is more common, but lung dose is positively associated with the incidence and severity of RP 31 – 33 . Therefore, breast cancer patients who received extra RNI have a significantly higher rate of RP than those who received whole breast radiotherapy alone 34 , 35 . In this study, V500cGy (from 53.3 ± 3.0% to 48.3 ± 2.9%, p < 0.05), V2000cGy (from 25.7 ± 1.9% to 20.6 ± 3.2%, p < 0.05), V3000cGy (from18.3 ± 2.5% to 15.3 ± 2.3%, p < 0.05), and mean dose (from 1332.1 ± 128.7cGy to 1165.4 ± 148cGy, p < 0.05) were decreased to different degrees. The V3000cGy of the ipsilateral lung decreased to less than 20% in all patients. The results of this study further proves the feasibility and necessity of using DIBH to reduce pulmonary exposure during RNI-containing right breast radiotherapy. Among the OARs involved in this study, liver changed the most in terms of mean dose (916.9 ± 318. 9cGy to 281.2 ± 150.3 cGy) and average dose reduction rate(69.4%). Although radiation-induced liver toxicity has been widely recognized, the related research in breast cancer radiotherapy is still insufficient. Only a few radiotherapy planning studies have shown that DIBH technique can achieve good liver protection effect in right breast cancer 23 , 24 , 37 . In the DIBH state, the increase of lung volume makes the liver deviate from the target volume to the human foot side, which is the direct reason for the significant reduction of liver dose. Although the evidence related to the clinical benefit of liver protection in breast cancer radiotherapy is still short, according to the ALARA principle, DIBH potential benefit value for liver protection of the right breast cancer radiotherapy patients is still positive. With the development of DIBH radiotherapy technology, the repeatability and stability of interfractional and intrafractional breath holding have been widely concerned 38 – 42 . SGRT-based DIBH radiotherapy adopts optical image-guided positioning to improve the setup accuracy before treatment, and to monitor patients' position changes in real time during treatment, which enhances the repeatability and stability of patients' breath-holding and effectively guarantees treatment accuracy for patients 40 – 43 . Amid the implementation of SGRT-based DIBH radiotherapy, the position of the respiratory gating primary point can be manual placed. In most of the reported studies, the position of the gating primary point is not clear, and there is a lack of relevant comparative studies to guide the set up of the gating primary point 14,15,43−45 . AAPM Task Group Report 302 believes that a better respiratory curve can be obtained when the gating point is placed at the xiphoid process 43 . D.Reit Z et al 44 analysed the breath-hold stability and repeatability of 6013 DIBH fractional treatment. In that study, all patients' gating primary points were placed at the edge of xiphoid process, and the breath-hold amplitude displayed by the SGRT system between patients' fractional treatment was used as an indicator to judge the breath-hold stability and repeatability. Schönecker et al 45 reported that DIBH radiotherapy for left breast cancer has also been performed by setting gating primary points on the sternum. Among the 31 patients included in this study, the gating primary points of the patients undergoing breast-conserving surgery were placed on the edge of xiphoid process (11 cases) or the middle of sternum (12 cases), and 8 cases of the patients undergoing radical mastectomy surgery were set on the contralateral breast wall where the bolus was avoided. The research team compared and analysed the CBCT validation data collected from 187 fractions in 31 patients under DIBH after dividing them into three groups (EXP group, SM group, LBW group), and performed a retrospective evaluation study on the treatment accuracy. The statistical results of the three sets of data showed that, in the SM group and LBW group, the overall setup errors in all directions were 2.4 ± 3.0mm and 2.5 ± 3.2mm, respectively. The incidence of absolute setup errors within 3mm was 64.1% and 59.8%, respectively and meanwhile, only one fraction showed setup error greater than 8mm in both groups, with an occurrence rate of less than 1%. This indicated that the SM group and LBW group had better breath-hold repeatability and stability, and in turn higher treatment accuracy. Whereas, in EXP group, the overall setup error in all directions was 3.2 ± 4.0mm, the incidence of the absolute value of setup error within 3mm was 52.6% and 6 fractions showed abnormal setup error greater than 8mm, five of them clustered in AP direction. Through the analysis of these abnormal data on CBCT images, it was found that inspiratory capacity seriously insufficient occured in 4 patients, and the positions of heart, lung and liver were significantly inconsistent with those of localization CT images, as shown in Fig. 3 .This is an important finding, and although all patients were trained to perform thoracic breathing and were performed CBCT scans while holding their breath to a preset range of gating windows, abnormal breath-hold stability and repeatability persisted. After analysis, the research team believes that the rise in respiration at the edge of xiphoid process is affected by both the amplitude of thoracic and abdominal respiration, and during the course of treatment, patients involuntarily adopt abdominal or mixed breathing to make the breathing amplitude reach the preset range of the gating window, which leads to the relatively poor treatment accuracy of EXP group in this study. For patients with thoracic breathing, the gating point placed on the sternum or breast wall has better interfractions breath-holding repeatability and stability, and the EXP gating point needs to be carefully selected. DIBH radiotherapy for right breast cancer has high overall treatment accuracy under the premise of selecting appropriate gating point location. The analysis of regional anatomical location accuracy is not studied in this paper, which will be concerned in subsequent studies. Theoretically, the location selection of gating points is equally important to ensure the accuracy of DIBH radiotherapy for left and right breast cancer. If conditions permit, abdominal pressure technique can be used in thoracic breathing to control the occurrence of abdominal breathing. In addition, we observed large differences in DIBH height when different gating points were placed. Statistics showed that the DIBH heights of the EXP, SM and LBM groups were 13.5 ± 3.7mm, 10.3 ± 2.4mm, and 9.6 ± 2.8mm, respectively and the difference was statistically significant (P < 0.05). The corresponding right lung volume increment was 71.3%, 69.9%, and 67.2%, respectively(P = 0.08), without statistically significant difference. Although the breath-hold height of EXP group was significantly higher than that of the other two groups, the lung volume increase rate was larger in all three groups without significant difference. Oonsiri et al 47 studied the correlation between total lung volume (TLV), central lung distance (CLD), chest wall separation (CWS) and DIBH radiotherapy exclusion criteria for left breast cancer, and found that there was a deterministic relationship between TLV increment and cardiopulmonary dose decrease. The mean increase in lung volume in that study was 41.5%, which can be used as an exclusion criterion for DIBH radiotherapy. In traditional DIBH breathing training, the rise height of the gating point after breathing is generally considered as an important indicator for predicting lung volume increase. Schröde et al 46 did not specify the position of the gating point during the clinical workflow of DIBH, but required that the rise height of the DIBH gating point be greater than 12m from the baseline. In this study, in the SM group and LBW group with better breath-holding repeatability and stability, a total of 11 patients did not reach 12mm in respiration height, the lowest of which was only 6.5mm, and the right lung volume increment of the patients was above 50%, which was higher than that in Oonsiri 47 and other studies. Retrospective planning data in Table 1 also confirmed dosimetric benefits of varying degrees in these patients. We believes that the body surface rise of patients after DIBH varies greatly with different patients and different gating points. If breath-hold height is used as a reference index to evaluate lung volume increment and furthermore emerges as the exclusion criterion for DIBH radiotherapy, it is necessary to further study and clarify the specific reference values corresponding to different gating point locations. Until then, it is still recommended to observe the anatomical position changes and calculate the lung volume increment by scanning FB and DIBH CT images for accurate determination. The results of previous radiotherapy planning studies suggested that patients receiving right breast radiotherapy with RNI had significant benefit in heart and lung dosimetry, while patients receiving right breast radiotherapy without RNI had less benefit 22 – 26 . To this end, DIBH radiotherapy was only applied to right breast cancer with RNI for this retrospective study. The results of this study confirmed the restricted effect of DIBH radiotherapy supported by optical surface images on OARs dose(especially liver) and proved that, DIBH technique had high therapeutic accuracy in right breast cancer. In the future, DIBH radiotherapy in right breast cancer without RNI will be studied, so as to explore its broader clinical application value. Conclusion Although DIBH radiotherapy has rarely been reported in right-sided breast cancer, a small number of radiotherapy planning studies have shown its potential benefits, especially in right-sided breast cancer patients with RNI. This study based on real treatment data performed retrospective analysis, which reckoned that on the premise of reasonable technology, SGRT-based DIBH technique could better protect patients' hearts, lungs and livers after its application to RNI-containing right breast cancer and interfractions/intrafractions had high repeatability and stability to ensure high precision, which is suggested to be popularized. Abbreviations deep inspiration breath hold (DIBH); regional nodal radiation (RNI); surface guided radiotherapy (SGRT); Free breath (FB); organs at risk (OARs); edge of xiphoid process (EXP); sternum middle (SM); left breast wall (LBW); cone beam CT (CBCT); gross tumor volume (GTV); clinical target volume (CTV); Declarations Ethics approval and consent to participate The study was conducted in accordance with the Declaration of Helsinki, and approved by the Ethics Committee of Zhejiang hospital (protocol code 2022(105k) and date of 26,09,2022). Consent for publication Not applicable. Availability of data and materials The data presented in this study are available on request from the corresponding author. The data are not publicly available due to patients, privacy. Competing interests The authors declare no conflict of interest. Funding This work was supported in part by the Zhejiang Public Welfare Research Program under Grant LGF20H160020, and in part by the Zhejiang Medical and Health Science and Technology Project under Grant 2022PY078. Authors' contributions Conceptualization, Jianjun Lai and Haili Hu; methodology, Lu Jiang; data analysis, Jing Wu, Lan Lei and Chuanfeng Zhang; writing—original draft preparation, Jianjun Lai ; writing—review and editing, Zhao Jing and Zhibing Wu; supervision, Li qu; All authors have read and agreed to the published version of the manuscript. Acknowledgements Not applicable. References Lei S, Zheng R, Zhang S. et al . Global patterns of breast cancer incidence and mortality: A population-based cancer registry data analysis from 2000 to 2020. Cancer Commun (Lond). 2020;41:1183–94. Siegel RL, Miller KD, Fuchs HE. et al . Cancer statistics2022.CA:A Cancer. J Clin. 2022;72:7–33. Sung H, Ferlay J, Siegel RL. et al . Global Cancer Statistics2020:GLOBOCAN Estimates of Incidence and Mortality Worldwide for 36 Cancers in 185 Countries. CA:A Cancer Journal for Clinicians. 2021;71:209–49. Loibl S, Poortmans P, Morrow M. et al Breast cancer Lancet. 2021;397:1750–69. Yang SX, Polley EC. Systemic treatment and radiotherapy, breast cancer subtypes,and survival after long-term clinical follow-up. Breast Cancer Res Treat. 2019;175:287–95. Buchholz TA. Increasing the value of radiotherapy in breast cancer. Lancet Oncol. 2021;22:572–3. Luo J, Jin K, Chen X. et al . Internal Mammary Node Irradiation (IMNI) Improves Survival Outcome for Patients With Clinical Stage II-III Breast Cancer After Preoperative Systemic Therapy. Int J Radiat Oncol Biol Phys. 2019;103:895–904. Whelan TJ, Olivotto IA, Parulekar WR. et al . Regional nodal irradiation in early-stage breast cancer. N Engl J Med. 2015;373:307–16. Hayden AJ, Rains M, Tiver K. et al . Deep inspiration breath hold technique reduces heart dose from radiotherapy for left-sided breast cancer. J Med Imaging Radiat Oncol. 2012;56:464–72. Simonetto C, Eidemüller M, Gaasch A. et al . Does deep inspiration breath-hold prolong life?Individual risk estimates of ischemic heart disease after breast cancer radiotherapy. Radiother Oncol. 2019;131:202–7. Dumane VA, Saksornchai K, Zhou Y. et al . Reduction in low-dose to normal tissue with the addition of deep inspiration breath hold(DIBH) to volumetric modulated arc therapy (VMAT) in breast cancer patients with implant reconstruction receiving regional nodal irradiation. Radiat Oncol. 2018;13:187–94. Pandeli C, Smyth LML, David S. et al . Dose reduction to organs at risk with deep-inspiration breath-hold during right breast radiotherapy:a treatment planning study. Radiat Oncol. 2019;14:223. Conway JL, Conroy L, Harper L. et al . Deep Inspiration Breath-Hold (DIBH) produces a clinically meaningful reduction in ipsilateral lung dose during loco-regional radiation therapy for some women with right-sided breast cancer. Practical Radiation Oncology. 2017;7:147–53. Essers M, Poortmans PM, Verschueren K. et al . Should breathing adapted radiotherapy also be applied for right-sided breast irradiation? Acta Oncol. 2016;55:460–5. Laaksomaa M, Sarudis S, Rossi M. et al . AlignRT® and Catalyst™ in whole-breast radiotherapy with DIBH:Is IGRT still needed? J Appl Clin Med Phys. 2019;20:97–104. Li Xa, Tai A, Arthur DW. et al . Variability of target and normal structure delineation for breast cancer radiotherapy:an RTOG multi-institutional and multiobserver study. Int J Radiat Oncol Biol Phys. 2009;73:944–51. Darby SC, Ewertz M, McGale P. et al . Risk of ischemic heart disease in women after radiotherapy for breast cancer. N Engl J Med. 2013;368:987–98. Alonso C, Showalter S, Neal B. et al . Comparison of Heart Dose in Early Stage Left Sided Breast Cancers Treated with IORT or EBRT-DIBH. Int J Radiat Oncol Biol Phys. 2017;99(2):E1–2. Simonetto C, Eidemüller M, Gaasch A. et al . Does deep inspiration breath-hold prolong life? Individual risk estimates of ischemic heart disease after breast cancer radiotherapy. Radiother Oncol. 2019;131:202–7. Loap P, Goudjil F, Baron B. et al . Deep Inspiration Breath-Hold (DIBH) for Locoregional Breast Irradiation using Volumetric Modulated Arc Therapy (VMAT) and Intensity Modulated Proton Therapy (IMPT): A Dosimetric Comparison to Cardiac Substructure-ScienceDirect. Int J Radiat Oncol Biol Phys. 2020;108:e43. Yang D, Piao Y, Yuan F. et al . Gastric side effects and the stomach dosimetric analysis in left-sided breast cancer radiotherapy in free-breathing and deep inspiration breath-hold technique. Radiat Oncol. 2022;17:1–9. Peters GW, Gao SJ, Knowlton C. et al . Benefit of Deep Inspiratory Breath Hold for Right Breast Cancer When Regional Lymph Nodes Are Irradiated. Practical Radiation Oncology. 2022;12:e7–12. Pandeli C, Smyth LML, David S. et al . Dose reduction to organs at risk with deep-inspiration breath-hold during right breast radiotherapy: a treatment planning study. Radiat Oncol. 2019;14:223. Remouchamps VM, Vicini FA, Sharpe MB. et al . Significant reductions in heart and lung doses using deep inspiration breath hold with active breathing control and intensity-modulated radiation therapy for patients treated with locoregional breast irradiation. Int J Radiat Oncol Biol Phys. 2003;55:392–406. Prabhakar R, Tharmar G, Julka PK. et al . Impact of different breathing conditions on the dose to surrounding normal structures in tangential field breast radiotherapy. J Med Phys. 2007;32:24–8. Nissen HD, Appelt AL. Improved heart, lung and target dose with deep inspiration breath hold in a large clinical series of breast cancer patients. Radiother Oncol. 2013;106:28–32. Essers M, Poortmans PM, Verschueren K. et al . Should breathing adapted radiotherapy also be applied for right-sided breast irradiation? Acta Oncol. 2016;55:460–5. Stowe HB, Andruska ND, Reynoso F. et al . Heart Sparing Radiotherapy Techniques in Breast Cancer: A Focus on Deep Inspiration Breath Hold. Breast Cancer (Dove Med Press. 2022;14:175–86. Altınok A, Askeroğlu O, Doyuran M. et al . Dosimetric evaluation of right coronary artery in radiotherapy for breast cancerr. Med Dosim. 2019;44:205–9. Grantzau T, Overgaard J. Risk of second non-breast cancer after radiotherapy for breast cancer: a systematic review and meta-analysis of 762468 patients. Radiother Oncol. 2015;114:56–65. Marks LB, Yu X, Vujaskovic Z. et al . Radiation-induced lung injury. Semin Radiat Oncol. 2003;13:333–45. Marks LB, Bentzen SM, Deasy JO. et al . Radiation dose-volume effects in the lung. Int J Radiat Oncol Biol Phys. 2010;76:70–6. Rothwell RI, Kelly SA, Joslin CAF. Radiation pneumonitis in patients treated for breast cancer. Radiother Oncol. 1985;4:9–14. Matzinger O, Heimsoth I, Poortmans P. et al . Toxicity at three years with and without irradiation of the internal mammary and medial supraclavicular lymph node chain in stage I to III breast cancer (EORTC trial 22922/10925). Acta Oncol. 2010;49:24–34. Choi J, Kim YB, Shin KH. et al . Radiation pneumonitis in association with internal mammary node irradiation in breast cancer patients: an ancillary result from the KROG08-06 study. J Breast Cancer. 2016;19:275–82. Pan CC, Kavanagh BD, Dawson LA. et al .Quantitative analysis of normal tissue effects in the clinic:radi-ation-associated liver injury. Int J Radiat Oncol Biol Phys. 2010;76:94–100. Prabhakar R, Tharmar G, Julka PK. et al . Impact of different breathing conditions on the dose to surrounding normal structures in tangential field breast radiotherapy. J Med Phys. 2007;32:24–8. Nguyen K, Gonzalez V. Daily Set-up Reproducibility of Three-Field Breast Technique in Conjunction With Deep Inspiratory Breath Hold (DIBH). Int J Radiat Oncol Biol Phys. 2015;93:E2. Ranger A, Dunlop A, Grimwood A. et al . Voluntary versus ABC breath-hold in the context of VMAT for breast and locoregional lymph node radiotherapy including the internal mammary chain. Clin Transl Radiat Oncol. 2021;27:164–8. Garcia R, Mazars P, Jaegle E. et al . EP-2026: Breast Radiotherapy:Heart position reproducibility with spirometric DIBH. RADIOTHER ONCOL. 2018;127:1106–7. Russo S, Rossi F, Stoppa G. et al . EP-1631:Reproducibility of DIBH tecnique guided by an optical system: the florence usl experience. RADIOTHER ONCOL. 2017;123:s884. Rossi F, Russo S, Barca R. et al . EP-1773: Dosimetric benefits and reproducibility of DIBH tecnique guided by an optical system. RADIOTHER ONCOL. 2016;119:831. Al-Hallaq HA, Cerviño L, Gutierrez AN. et al . AAPM task group report 302:Surface-guided radiotherapy. MED PHYS. 2022;49:e82–112. Reitz D, Walter F, Schönecker S. et al . Stability and reproducibility of 6013 deep inspiration breath-holds in left-sided breast Cancer. Radiat Oncol. 2020;15:121. Schönecker F, Walter P, Freislederer C. et al . Treatment planning and evaluation of gated radiotherapy in left-sided breast cancer patients using the Catalyst TM /Sentinel™ system for deep inspiration breath-hold (DIBH) . Radiat Oncol. 2016;11:143–53. Schröder C, Kirschke S, Blank E. et al . Deep inspiration breath-hold for patients with left-sided breast cancer-A one-fits-all approach? A prospective analysis of patient selection using dosimetrical and practical aspects. Br J Radiol. 2022;95:20210295. Dell'Oro M, Giles E, Sharkey A. et al . A Retrospective Dosimetric Study of Radiotherapy Patients with Left-Sided Breast Cancer; Patient Selection Criteria for Deep Inspiration Breath Hold Technique. Cancers (Basel). 2019;11:259. Additional Declarations No competing interests reported. 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Also discoverable on Platform About Our Team In Review Editorial Policies Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-2185678","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":145923049,"identity":"35041663-dcd4-4b3a-beef-332c774e1260","order_by":0,"name":"Jianjun Lai","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAxUlEQVRIiWNgGAWjYBACefb+hw8SKmyY7dsbiNRi2HOG2eDDmTR2A54DxFpzI4dNcmbLYX4DiQQidTD2nD1szNtwWNpc8vHGGww1NtEEtbCz9yU+5t2Rbmw5O63YguFYWm4DYVsOGBvznrFOZridYybB2HCYsBaGGwlm0rxtzPUNN88QrSXHTHJmmzOzwQ0eIrUY9hxLBgUys2QP0C8JxPhFnr35IDgq+dkPb7zxocaGCIchAeKjBkkLqTpGwSgYBaNgZAAAl45C5VbXdnQAAAAASUVORK5CYII=","orcid":"","institution":"Zhejiang Hospital","correspondingAuthor":true,"submittingAuthor":false,"prefix":"","firstName":"Jianjun","middleName":"","lastName":"Lai","suffix":""},{"id":145923050,"identity":"3deaaacd-3544-4959-b687-c5e6cd0c0b1f","order_by":1,"name":"Haili Hu","email":"","orcid":"","institution":"Zhejiang Hospital","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Haili","middleName":"","lastName":"Hu","suffix":""},{"id":145923051,"identity":"37085149-fc26-419c-a88d-8a59c1531771","order_by":2,"name":"Lu Jiang","email":"","orcid":"","institution":"Zhejiang Hospital","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Lu","middleName":"","lastName":"Jiang","suffix":""},{"id":145923052,"identity":"17dfa1dc-7f21-49c7-8bf1-b5712a6db3c4","order_by":3,"name":"Jing Wu","email":"","orcid":"","institution":"Zhejiang Hospital","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Jing","middleName":"","lastName":"Wu","suffix":""},{"id":145923053,"identity":"a1009342-a16e-4f1a-99c0-90f0b542876d","order_by":4,"name":"Lan Lei","email":"","orcid":"","institution":"Zhejiang Hospital","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Lan","middleName":"","lastName":"Lei","suffix":""},{"id":145923054,"identity":"6d906144-cd42-443f-a60e-37de07192991","order_by":5,"name":"Chuanfeng Zhang","email":"","orcid":"","institution":"Zhejiang Hospital","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Chuanfeng","middleName":"","lastName":"Zhang","suffix":""},{"id":145923055,"identity":"c2d3c17d-60df-4d1d-a00a-07745429dc59","order_by":6,"name":"Zhao Jing","email":"","orcid":"","institution":"Zhejiang Hospital","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Zhao","middleName":"","lastName":"Jing","suffix":""},{"id":145923056,"identity":"f54631a4-9119-4f40-9c4e-7624a6a8906e","order_by":7,"name":"Li Qu","email":"","orcid":"","institution":"Zhejiang Hospital","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Li","middleName":"","lastName":"Qu","suffix":""},{"id":145923057,"identity":"ce51b5b8-1b59-4bb7-90b8-6733f9730c6a","order_by":8,"name":"Zhibing Wu","email":"","orcid":"","institution":"Zhejiang Hospital","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Zhibing","middleName":"","lastName":"Wu","suffix":""}],"badges":[],"createdAt":"2022-10-20 07:59:26","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-2185678/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-2185678/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":28235904,"identity":"10ec8024-96a4-40c7-954b-31a37cca08e9","added_by":"auto","created_at":"2022-10-25 15:40:18","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":120227,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic overview of the clinical workflow. EXP, SM, and LBW represent the gating points placed on edge of xiphoid process, sternum middle and left breast wall respectively. CBCT=cone beam CT; DIBH=Deep inspiration breath hold; FB=Free breath; SGRT=surface guided radiotherapy.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-2185678/v1/27b5ad50021560573d31a787.png"},{"id":28235905,"identity":"4e7e5d2d-af5a-4f2b-bdab-04dc8cd457be","added_by":"auto","created_at":"2022-10-25 15:40:18","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":104505,"visible":true,"origin":"","legend":"\u003cp\u003eBoxplots of treatment planning data for organs at risk (OARs), for the 31 breast cancer patients included in this study, with deep inspiration breath-hold (DIBH), free breath (FB) and 4-7 fields tangential IMRT (tIMRT).\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-2185678/v1/0bbd33f4fb49349b8e05134e.png"},{"id":28235906,"identity":"e8b76686-6c84-4405-8298-2d194be1ccde","added_by":"auto","created_at":"2022-10-25 15:40:19","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":188627,"visible":true,"origin":"","legend":"\u003cp\u003eThe pictures(A, B, C and D, E, F) show \u0026nbsp;setup CBCT verification images of a right breast cancer patient in two differents fractions with deep inspiration breath-hold(DIBH) under the gating points placed on EXP. The transverse plane image(A) showed that insufficient inspiratory volume resulted in excessive setup error in AP direction during treatment, and the sagittal and coronal plane images(B and C) showed that insufficient inspiratory volume led to large differences in liver position. But in another fraction, CBCT images(D, E and F) show a successful raditherapy fraction with great DIBH reproducibility.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-2185678/v1/c10f318141a7944921b708ec.png"},{"id":29875860,"identity":"cfb620ae-9d77-45e8-a49f-989c3f6fc629","added_by":"auto","created_at":"2022-12-04 21:59:32","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":982810,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-2185678/v1/a07ee23a-15e1-4433-996e-bfbb201c66f7.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"SGRT-based DIBH radiotherapy practice for right breast cancer combined with RNI: A retrospective study on dosimetry and treatment accuracy","fulltext":[{"header":"Background","content":"\u003cp\u003eIn recent years, breast cancer has become the most common malignant tumor in women worldwide\u003csup\u003e\u003cspan additionalcitationids=\"CR2\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e. Existing mainstream treatment mode for breast cancer is still a comprehensive treatment mode including surgery, chemotherapy, radiotherapy, targeted therapy and gene therapy\u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e,\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u003c/sup\u003e. Postoperative combined radiotherapy can reduce the local and distant recurrence rate, improve the local control rate and mend the prognosis for patients\u003csup\u003e\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e,\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e. In radiotherapy for breast cancer, organs at risk (OARs) and normal tissues around the target region are typically irradiated to a certain extent. Especially for patients with regional nodal radiation (RNI), the larger irradiation region always inevitably expands the volume of normal tissues exposed to radiation while increasing therapeutic benefit, which in turn cranks up the risk of toxicity\u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e,\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eDeep inspiration breath hold (DIBH) can significantly ameliorate the risk of cardiotoxicity in patients with left breast radiotherapy, reduce the irradiation dose to the heart and its substructures amid left breast radiotherapy\u003csup\u003e\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e,\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e, and benefit for the lung,liver and stomach to varying degrees\u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e,\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e. Although DIBH is widely used in radiotherapy of left breast cancer, it is rarely used in radiotherapy for right breast cancer. Only a few scholars have performed dosimetric studies through the planning system.These studies show that DIBH can benefit for different patients in radiotherapy of right breast cancer to different degrees. In particular for patients with RNI, DIBH can significantly reduce the maximum dose of right coronary artery (RCA) and the volume of liver exposured at low dose\u003csup\u003e\u003cspan additionalcitationids=\"CR13\" citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eThe use of optical surface imaging technology in respiratory controlled radiotherapy can dynamically monitor the body surface position and respiratory movement data for patients in real time, which has the characteristics of non-radiation and high precision and is widely popular in DIBH gating radiotherapy for breast cancer\u003csup\u003e\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e,\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e. Since May 2021, the department to which the author belongs had been using surface guided radiotherapy (SGRT) based DIBH radiotherapy for postoperative right breast cancer patients with RNI, and the author had been making retrospective study on the dosimetry and accuracy (repeatedly and stability) of SGRT-based DIBH radiotherapy pursuant to real treatment data, which aims to expound the clinical application value and related issues of this technique in RNI-containing radiotherapy for right breast cancer.\u003c/p\u003e"},{"header":"Materials And Methods","content":"\u003cp\u003eThe inclusion criteria were patients who received RNI-containing right breast radiotherapy (after breast-conserving or radical surgery), had good compliance, and completed the entire DIBH treatment process. A total of 31 patients were screened, including 21 breast-conserving patients and 10 radical surgery patients, with an average age of 50.2 years (range:29\u0026ndash;72 years). Figure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e shows clinical treatment process of patients, including respiratory gating primary point setup, respiratory training, CT and optical surface image acquisition, treatment planning, setup and delivery, CBCT position verification and problem handling mechanism.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003elmmolilization, primary point setup and CT simulation\u003c/h2\u003e \u003cp\u003eFor patients who were to receive DIBH radiotherapy for right breast cancer, individualized negative pressure vacuum bag molds were made for postures fixation and a laser-based surface scanner (Sentinel\u0026trade;, C-RAD AB, Sweden) was mounted on the localized CT end for respiratory gating operation. The respiratory gating primary point for breast-conserving patients were placed at the lower edge of the xiphoid process or the middle sternum. The gating primary point for radical surgery patients was set on the lateral wall of the left breast to avoid the bolus. Patients were trained to perform thoracic breathing, the width of the gating window at the primary point was 1.5-3mm, and it was reckoned that DIBH requirements were met when breath-holding duration was 20s and could be repeated for more than three consecutive times. 3mm CT images were acquired under FB and DIBH using a CT simulator (Somatom, Simenz, Germanny), reference images of the body surface under FB were acquired using Sentinel\u0026trade; and sent to the accelerator end of optical-based surface scanner (Catalyst\u0026trade;, C-Rad AB,Sweden) together with the gating window parameters, and lung volume under FB and DIBH was delineated on CT images using an automatic segmentation tool. According to Oonsiri et al\u003csup\u003e\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e\u003c/sup\u003e reported and the previous DIBH practice experience for left breast cancer, the target volume of FB and DIBH should be delineated and planned simultaneously on the premise that the right lung volume under DIBH is greater than 50% of the right lung volume under FB.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003eTarget volume and organ at risks delineation, treatment and planning\u003c/h2\u003e \u003cp\u003eFor the same patient, the same radiation oncologist delineated the OARs target volume on the CT images under FB and DIBH simultaneously. The gross tumor volume (GTV) and clinical target volume (CTV) were delineated according to the Radiation Therapy Oncology Group(RTOG) standard. PTV and PGTV were defined as the expansion of CTV and GTV by 10mm and the retraction to 5mm subcutaneously, respectively. The heart and liver were automatically generated by an automated segmentation tool and reviewed and manually adjusted by a radiation oncologist, and the RCA was manually delineated.\u003c/p\u003e \u003cp\u003eThe prescription dose of PTV was 5000cGy in 25 fractions in all patients, and PGTV was added to 5750cGy in 25 fractions for patients after breast conservation. The target volume dose-volume criteria were as recommended by ICRU as follows: Maximum dose of not exceeding 107%, coverage of PTV/PGTV by the 95% isodose. FB and DIBH radiotherapy plans were designed by the same radiotherapy physicist using 6MV-FFF ray energy for the same patient, and 4\u0026ndash;7 tangential IMRT fields based on DMLC technology were used depending on the complexity of the plans. All patients underwent Monte Carlo dose calculation on the radiotherapy planning system (Monaco5.1, Elekta, Sweden). QUANTEC guidelines were used to limit and determine OARs dose-volume, and the dose and volume were kept as low as possible. Both FB and DIBH radiotherapy plans were reviewed and approved by the radiation oncologists. After confirming that the DIBH plan was overall superior to the FB plan,the DIBH radiotherapy plan was sent to the linear accelerator (LA) end (Infinity\u0026trade;,Elekta,Sweden) for plan verification and treatment.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003eSetup and treatment implementation\u003c/h2\u003e \u003cp\u003eFor the first treatment, after the laser line in the treatment room was aligned to the body surface marker line of patients under FB, the position was verified using an optical-based surface scanner (Catalyst\u0026trade;, C-RAD AB, Sweden) at the LA end. The verification criteria are the deviation of translation\u0026thinsp;\u0026le;\u0026thinsp;3mm and the deviation of rotation\u0026thinsp;\u0026le;\u0026thinsp;2\u0026deg;. Optical reference images were subsequently re-acquired under FB using Catalyst\u0026trade; after position verification and calibration with CBCT under DIBH. In day-to-day treatment, both body surface marker and optical image positioning were performed according to the first treatment. CBCT was used to verify and calibrate the position under DIBH once a week and to re-collect FB optical reference images. In case of abnormal setup data in CBCT, the position re-verification by CBCT after adjusting position and breathing, which under DIBH mode was also checked before the treatment of the next day. All patients treatment with DIBH were triggered by the Response\u0026trade; gating interface within a preset gating window for linear accelerator beam-on therapy. The Catalyst\u0026trade; was used to monitor displacement in real time during treatment.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003eStatistical analysis for dosimetric data and setup accuracy data\u003c/h2\u003e \u003cp\u003eMann-Whitney U tests were used to analyse differences in the dose-volume constraints achieved of OARs between the FB and DIBH plans, which is suitable for data which are not normally distributed as confirmed by the Shapiro-Wilk test. Kruskal-Wallis H tests were used to analyse differences in multiple groups of sample data, which is also applicable to data which are not normally distributed as confirmed by the Shapiro-Wilk test. The statistical tests were conducted using SPSS27.0 and p\u0026thinsp;\u0026lt;\u0026thinsp;0.05 was considered to be statistically significant.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eDosimetric statistics for all DIBH and FB treatment plans\u003c/h2\u003e \u003cp\u003eIn this study, FB and DIBH dosimetric data were collected from 31 right breast cancer patients having completed radiotherapy with DIBH. Coverage of PTV by 95% isodose and coverage of PGTV by 95%-100% isodose were set for both treatment plans. Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e summarizes the dose-volume data of four OARs under the premise that the dose-volume requirements of PTV and PGTV are met. Figure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e shows the boxplot comparison of the dose-volume data of OARs in 31 patients. The indicators related to target volume dose-volume between the two groups of data met the requirements and there was no statistical difference, while the difference of all OARs dose-volume between the two groups of data was statistically significant.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eSummary of treatment planning data for organs at risk, for the 31 right breast cancer patients included in this study, with deep inspiration breath-hold (DIBH)), free breath(FB) and 4\u0026ndash;7 fields tangential IMRT (tlMRT).\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eN\u0026thinsp;=\u0026thinsp;31\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eFB\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eDIBH\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e95%CI\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003ep\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eDescent rate(%)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHeart mean Dose(cGy)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e225.2\u0026thinsp;\u0026plusmn;\u0026thinsp;75.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e171.2\u0026thinsp;\u0026plusmn;\u0026thinsp;48.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e31.2ཞ96.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e༜0.05\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e25.2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHeart max Dose(cGy)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e1666.9\u0026thinsp;\u0026plusmn;\u0026thinsp;961.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e927.6\u0026thinsp;\u0026plusmn;\u0026thinsp;390.5\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e366.6ཞ1112.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e༜0.05\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e\u003cb\u003e44.3\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRAD mean Dose(cGy)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e444.8\u0026thinsp;\u0026plusmn;\u0026thinsp;161.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e342.4\u0026thinsp;\u0026plusmn;\u0026thinsp;112.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e31.8ཞ173.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e༜0.05\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e23.1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRAD max Dose(cGy)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e1090.9\u0026thinsp;\u0026plusmn;\u0026thinsp;569.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e581.1\u0026thinsp;\u0026plusmn;\u0026thinsp;165.7\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e296.7ཞ722.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e༜0.05\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e\u003cb\u003e46.7\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLung-R mean Dose(cGy)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e1332.1\u0026thinsp;\u0026plusmn;\u0026thinsp;128.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e1165.4\u0026thinsp;\u0026plusmn;\u0026thinsp;148.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e96.1ཞ237.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e༜0.05\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e12.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLung-R V500cGy(%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e53.3\u0026thinsp;\u0026plusmn;\u0026thinsp;3.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e48.3\u0026thinsp;\u0026plusmn;\u0026thinsp;2.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e3.5ཞ6.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e༜0.05\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e9.4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLung-R V2000cGy(%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e25.7\u0026thinsp;\u0026plusmn;\u0026thinsp;1.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e20.6\u0026thinsp;\u0026plusmn;\u0026thinsp;3.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e3.8ཞ6.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e༜0.05\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e19.2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLung-R V3000cGy(%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e18.3\u0026thinsp;\u0026plusmn;\u0026thinsp;2.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e15.3\u0026thinsp;\u0026plusmn;\u0026thinsp;2.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.7ཞ4.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e༜0.05\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e16.7\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLiver mean Dose(cGy)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e916.9\u0026thinsp;\u0026plusmn;\u0026thinsp;318.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e281.2\u0026thinsp;\u0026plusmn;\u0026thinsp;150.3\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e509.1ཞ762.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e༜0.05\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e\u003cb\u003e69.4\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eDosimetric data are shown as mean values with one standard deviation for OARs. Mann-Whitney U tests were used for dosimetric data, and p\u0026thinsp;\u0026lt;\u0026thinsp;0.05 was considered to be statistically significant. Most favourable value in deep inspiration breath hold was marked in bold.\u003c/p\u003e \u003cp\u003eDescent rate(%) was the average decline for dose-volume data of four OARs after patients holds breath by deep inhalation.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003eCardiac dose\u003c/h2\u003e \u003cp\u003eCompared with FB plan, DIBH declined the mean dose of heart and RCA by 54.0\u0026thinsp;\u0026plusmn;\u0026thinsp;16.7cGy and 22.4\u0026thinsp;\u0026plusmn;\u0026thinsp;49.5cGy, respectively (P\u0026thinsp;\u0026lt;\u0026thinsp;0.05), and the mean descent rates were 25.2% and 23.1%, respectively. The maximum dose of heart and RCA were decreased by 739.3\u0026thinsp;\u0026plusmn;\u0026thinsp;571.2cGy and 509.8\u0026thinsp;\u0026plusmn;\u0026thinsp;462cGy, respectively (P\u0026thinsp;\u0026lt;\u0026thinsp;0.05), and the average reduction rates were 44.3% and 46.7%, respectively. This suggested that DIBH technology had a large dose decline value and decline rate for the maximum dose for heart and RCA and in terms of mean value, there was a significant difference (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05), but the dose decline value was slightly low because the mean dose to the heart was controlled at a low level in the two different breathing modes. Only 2 patients had a decrease in mean cardiac dose of over 100cGy (131.1cGy, 100.2cGy) and 3 patients shrank its RCA dose by more than 200cGy (249cGy, 289cGy, 328cGy).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003ePulmonary dose\u003c/h2\u003e \u003cp\u003eAccording to dose-volume data of right lung in this study, compared with FB technique, DIBH reduced right lung V500cGy, V2000cGy, V3000cGy and the mean dose of all patients to varying degrees. V500cGy decreased from 53.3\u0026thinsp;\u0026plusmn;\u0026thinsp;3.0% to 48.3\u0026thinsp;\u0026plusmn;\u0026thinsp;2.9%, V2000cGy went down from 25.7\u0026thinsp;\u0026plusmn;\u0026thinsp;1.9% to 20.6\u0026thinsp;\u0026plusmn;\u0026thinsp;3.2% and V3000cGy slumped from 18.3\u0026thinsp;\u0026plusmn;\u0026thinsp;2.5% to 15.3\u0026thinsp;\u0026plusmn;\u0026thinsp;2.3%. The mean dose contracted by 166.7\u0026thinsp;\u0026plusmn;\u0026thinsp;19.9cGy. In FB mode, there were 9 patients whose V3000cGy exceeded 20%, which compared with 31 patients whose V3000cGy was controlled below 20% by DIBH technique.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003eLiver\u003c/h2\u003e \u003cp\u003eThe mean liver dose using FB technique was 916.9\u0026thinsp;\u0026plusmn;\u0026thinsp;318.9cGy, and the mean liver dose exceeded l000cGy in 4 patients. After using DIBH technique, the mean liver dose was only 281.2\u0026thinsp;\u0026plusmn;\u0026thinsp;150.3cGy, an average decrease of 69.4%. Of all 31 patients enrolled in this study, the mean liver dose of 3 patients decreased by more than l000cGy (1160cGy, l005cGy, 1149cGy), the mean liver dose of 4 patients was controlled below l00cGy (82cGy, 91cGy, 78cGy, 99cGy). This manifested that DIBH significantly decreased the mean liver dose for patients with RNI-containing right breast cancer.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003eComparison of position accuracy under different DIBH gating primary points\u003c/h2\u003e \u003cp\u003eThe treatment accuracy study involved the setup error data calculated from 178 CBCT images in DIBH mode of 31 patients, including 78 in EXP group, 65 in SM group and 44 in LBW group. Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e shows the absolute value statistical results of three-dimensional setup errors under three different gating primary points placement conditions. When the DIBH gating primary points were placed on the edge of xiphoid process, sternum middle and contralateral breast wall, the corresponding overall positioning errors were 3.2\u0026thinsp;\u0026plusmn;\u0026thinsp;4.0mm, 2.4\u0026thinsp;\u0026plusmn;\u0026thinsp;3.0 m and 2.5\u0026thinsp;\u0026plusmn;\u0026thinsp;3.2mm, respectively. It is obvious that the setup accuracy of gating primary point at EXP was worse than that of the other two groups. The setup error in AP direction was 3.6\u0026thinsp;\u0026plusmn;\u0026thinsp;4.5mm at EXP, which was significantly higher than that of the other two groups (2.2\u0026thinsp;\u0026plusmn;\u0026thinsp;2.6mm, 2.4\u0026thinsp;\u0026plusmn;\u0026thinsp;3.1mm). In the SM group, the setup error interval of 0\u0026ndash;3 mm accounted for up to 64.1%, and the setup error of 8mm only occurred in one fraction(CC direction). In the LBW group, the setup error interval of 0-3mm made up 59.8%, and also the set up error of 8mm only occurred in one fraction (RL direction). The set up error ranging 0 to 3mm accounted for 52.6% in EXP group, and up to 6 fractions (2.6%) had the errors over 8mm, of which 5 times appeared in the AP direction. DIBH radiotherapy has a good treatment accuracy overall, but the location of the gating point has a certain impact on the treatment accuracy. The stability and repeatability of the fractional treatment are relatively poor when the gating point is placed at the edge of xiphoid process.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eSummary of setup error data for the 31 right breast cancer patients included in this study, with deep inspiration breath-hold (DIBH).\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eDirections\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eEXP(n\u0026thinsp;=\u0026thinsp;11,f\u0026thinsp;=\u0026thinsp;78)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eSM(n\u0026thinsp;=\u0026thinsp;12,f\u0026thinsp;=\u0026thinsp;65)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eLBW(n\u0026thinsp;=\u0026thinsp;8,f\u0026thinsp;=\u0026thinsp;44)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003ep\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"3\" rowspan=\"4\"\u003e \u003cp\u003eSetup error with any directions, mm\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAll direction\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e3.2\u0026thinsp;\u0026plusmn;\u0026thinsp;4.0\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.4\u0026thinsp;\u0026plusmn;\u0026thinsp;3.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.5\u0026thinsp;\u0026plusmn;\u0026thinsp;3.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e༜0.05\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAP direction\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e3.6\u0026thinsp;\u0026plusmn;\u0026thinsp;4.5\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.2\u0026thinsp;\u0026plusmn;\u0026thinsp;2.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.4\u0026thinsp;\u0026plusmn;\u0026thinsp;3.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e༜0.05\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCC direction\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3.3\u0026thinsp;\u0026plusmn;\u0026thinsp;4.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3.0\u0026thinsp;\u0026plusmn;\u0026thinsp;3.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.8\u0026thinsp;\u0026plusmn;\u0026thinsp;3.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e༜0.05\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eRL direction\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2.2\u0026thinsp;\u0026plusmn;\u0026thinsp;2.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.3\u0026thinsp;\u0026plusmn;\u0026thinsp;2.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.4\u0026thinsp;\u0026plusmn;\u0026thinsp;3.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e=\u0026thinsp;0.13\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"3\" rowspan=\"4\"\u003e \u003cp\u003eFractions with any excursion\u003c/p\u003e \u003cp\u003e\u0026isin;[0, 3) mm, no. (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAll direction\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e123(52.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e125(64.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e79(59.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e༜0.05\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAP direction\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e30(12.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e48(24.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e23(17.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e༜0.05\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCC direction\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e32(13.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e32(16.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e26(19.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e༜0.05\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eRL direction\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e59(25.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e45(23.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e30(22.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e༜0.05\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"3\" rowspan=\"4\"\u003e \u003cp\u003eFractions with any excursion\u003c/p\u003e \u003cp\u003e\u0026isin;[3, 8) mm, no. (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAll direction\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e105(44.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e69(35.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e52(38.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e༜0.05\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAP direction\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e40(17.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e17(8.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e14(10.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e༜0.05\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCC direction\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e45(19.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e32(16.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e18(13.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e༜0.05\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eRL direction\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e18(7.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e20(10.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e19(14.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e༜0.05\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"3\" rowspan=\"4\"\u003e \u003cp\u003eFractions with any excursion\u003c/p\u003e \u003cp\u003e\u0026isin;[8,\u0026infin;) mm, no. (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAll direction\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e6 (2.6)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1(0.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1(0.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e༜0.05\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAP direction\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e5(2.2)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0(0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1(0.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e༜0.05\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCC direction\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1(0.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1(0.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0(0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e༜0.05\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eRL direction\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0(0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0(0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0(0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e༜0.05\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"6\"\u003eAbsolute value of setup error data from CBCT are demoted as mean values with one standard deviation. Setup error data were not normally distributed as confirmed by the Shapiro-Wilk test, so Kruskal-Wallis H tests were used to analyse differences in setup error data statistics, and p\u0026thinsp;\u0026lt;\u0026thinsp;0.05 was considered to be statistically significant. Most favourable value in setup error is marked in bold. EXP, SM, and LBW represent the gating points placed on the edge of xiphoid process, sternum middle and left breast wall respectively. AP, CC and RL represent the anterior-posterior, cranio-caudal and right-left directions of the patients respectively.\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003eLung volume increment and gating primary point height\u003c/h2\u003e \u003cp\u003eThe right lung volume increment of 31 patients included in DIBH treatment process was \u0026ge;\u0026thinsp;50%. In EXP group, the increment averaged 72.3%. The height of corresponding gating window was 13.5\u0026thinsp;\u0026plusmn;\u0026thinsp;3.7 mm, with a height range of 9.2\u0026ndash;20.l mm; In SM group, the average increase was 69.9%, the height of the gating window was 10.3\u0026thinsp;\u0026plusmn;\u0026thinsp;2.4 mm, and the height range was 7.4-16.3mm. In the left breast wall group, the average increment was 67.2%. The height of the gating window was 9.6\u0026thinsp;\u0026plusmn;\u0026thinsp;2.8mm, and the height range was 6.5-14.6mm. The height of the gating window is recorded as the average value of the upper and lower threshold. All the three groups have good lung volume increment through DIBH, but the height of the gating window was significantly different (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05). In sternum middle and contralateral breast wall groups, the height of the gating window was significantly lower, which compared with that in the EXP group.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eSummary of height of gating window and corresponding right lung volume increment for the 31 right breast cancer patients included in this study, with deep inspiration breath-hold (DIBH).\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eEXP(n\u0026thinsp;=\u0026thinsp;11)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSM(n\u0026thinsp;=\u0026thinsp;12)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eLBW(n\u0026thinsp;=\u0026thinsp;8)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003ep\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLung-R volume\u003c/p\u003e \u003cp\u003efor FB (cm\u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1230.9\u0026thinsp;\u0026plusmn;\u0026thinsp;184.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1177.3\u0026thinsp;\u0026plusmn;\u0026thinsp;186.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1208.9\u0026thinsp;\u0026plusmn;\u0026thinsp;178.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e=\u0026thinsp;0.28\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLung-R volume\u003c/p\u003e \u003cp\u003efor DIBH (cm\u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2126.1\u0026thinsp;\u0026plusmn;\u0026thinsp;237.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1989.0\u0026thinsp;\u0026plusmn;\u0026thinsp;294.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2021.6\u0026thinsp;\u0026plusmn;\u0026thinsp;312.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e=\u0026thinsp;0.36\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLung-R volume Increment rate (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e72.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e69.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e67.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e=\u0026thinsp;0.08\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGating window\u003c/p\u003e \u003cp\u003eHeight (mm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e13.5\u0026thinsp;\u0026plusmn;\u0026thinsp;3.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e10.3\u0026thinsp;\u0026plusmn;\u0026thinsp;2.4\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e9.6\u0026thinsp;\u0026plusmn;\u0026thinsp;2.8\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e༜0.05\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"5\"\u003eLung-R volume and gating window height data are defined as mean values with one standard deviation. Volume and height data were not normally distributed as confirmed by the Shapiro-Wilk test, so Kruskal-Wallis H tests were used to analyse differences in volume and height data statistics, and p\u0026thinsp;\u0026lt;\u0026thinsp;0.05 was considered to be statistically significant. Most favourable value in gating window height is marked in bold. EXP, SM, and LBW represent the gating points placed on edge of xiphoid process, sternum middle and left breast wall respectively.\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eThe toxicity risk of breast cancer radiotherapy has been widely concerned by radiation oncologists. Darvby et al\u003csup\u003e\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u003c/sup\u003e showed that the incidence of major coronary events after breast cancer radiotherapy was linearly increased with the mean cardiac dose. For every l00cGy increase in the mean dose to the heart, the corresponding probability of coronary adverse events hiked by 7.4%, and the risk of cardiotoxicity lasted for decades after treatment. Colossal amounts of studies have shown that amid left breast cancer radiotherapy, DIBH technology can separate the heart from mammary gland position, so as to significantly shrink the high dose volume and mean dose of the heart, and reduce heart disease risks associated\u003csup\u003e\u003cspan additionalcitationids=\"CR19\" citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e. Meanwhile, coupled with DIBH technology, it can also increase the lung volume, reduce the lung tissue density, which lowers the irradiation dose in the lung\u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e, and slump the irradiation dose of the contralateral breast, stomach and liver to varying degrees\u003csup\u003e\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e,\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u003c/sup\u003e. Although DIBH technique is widely used in left-sided breast cancer, there are few reports on the clinical application of DIBH technique in right-sided breast cancer. According to several radiotherapy planning studies\u003csup\u003e\u003cspan additionalcitationids=\"CR24 CR25 CR26\" citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e, DIBH reduces lung dose compared with FB in patients with right-sided breast cancer and achieves liver protection during radiotherapy\u003csup\u003e\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eA radiotherapy planning study by Conway JL et al\u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e showed that the mean lung dose was reduced by 340cGy and the mean cardiac dose was significantly slumped in patients undergoing DIBH irradiation coupled with internal mammary chain (IMC). A radiotherapy planning study conducted by Chloe et al\u003csup\u003e\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e showed that 8 patients with RNI-containing right breast cancer were treated with DIBH technique. Their mean dose of the ipsilateral lung was decreased from 1820\u0026thinsp;\u0026plusmn;\u0026thinsp;320cGy to 1590\u0026thinsp;\u0026plusmn;\u0026thinsp;230 cGy, and maximum dose of RCA was reduced from 1160\u0026thinsp;\u0026plusmn;\u0026thinsp;720cGy to 560\u0026thinsp;\u0026plusmn;\u0026thinsp;290cGy. Although DIBH technology has obvious dosimetric value in right-sided breast radiotherapy, especially in the right breast with RNI irradiation, due to the complexity of the technology and the cost investment of time and labor, no large number of cases have been reported for clinical application. Abiding by 'as low as reasonably achievable'(ALARA) principle, DIBH radiation therapy for breast cancer patients with RNI had been conducted in our department since May 2021 and a retrospective study on dosimetry and accuracy for 31 breast cancer patients with RNI was conducted.\u003c/p\u003e \u003cp\u003eIn this study, the mean cardiac and RCA dose reduction rates by DIBH were 25.2% and 23.1%, respectively. However, the DIBH technique in left breast radiotherapy can reduce the mean dose of heart and LAD by 25\u0026ndash;67% and 20\u0026ndash;73%, respectively\u003csup\u003e\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e\u003c/sup\u003e, with an average reduction of 46% and 46.5%, respectively. In conclusion, in terms of the contribution of DIBH technology to the average decline rate for heart and RCA, the benefit of right breast cancer patients is significantly weaker than that of left breast cancer patients. It is speculated that, as the heart deviates from the right mammary gland, and the mean dose values of the heart and RCA are controlled at a low level under FB condition, although the distance between the heart and the chest wall is further increased by DIBH, its contribution to the mean reduction of the heart and its substructure is limited. With respect to maximum dose, DIBH technique significantly contracted the maximum dose of heart and RCA (decrease value: 740\u0026thinsp;\u0026plusmn;\u0026thinsp;570cGy, 510\u0026thinsp;\u0026plusmn;\u0026thinsp;460 cGy, P\u0026thinsp;\u0026lt;\u0026thinsp;0.05), and the average decline rates were 44.3% and 46.7%, respectively. The results of this study were similar to those of Chloe et al\u003csup\u003e\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e reported. A study by Altinok et al\u003csup\u003e\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e\u003c/sup\u003e showed that high doses of RCA in the heart, especially proximal part, increased the risk of coronary heart disease. During RNI irradiation, IMN is close to a small amount of heart volume, and DIBH technology can distance IMN from the heart, which significantly contributes to the reduction of the maximum dose of heart and RCA, and can reduce the risk of coronary heart disease in patients.\u003c/p\u003e \u003cp\u003eLung is an important OARs in breast cancer radiotherapy. In a meta-analysis of 742648 breast cancer patients, Grantzau and Overgaard\u003csup\u003e\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u003c/sup\u003e found that compared with patients who did not receive radiotherapy, patients accepted radiotherapy had a higher secondary lung cancer morbidity 5 and 15 years after treatment, 39% and 66% respectively. Due to advances in technology, the incidence of radiation pneumonitis (RP) after modern breast radiotherapy is lower (1%-5%) and pulmonary function decline is more common, but lung dose is positively associated with the incidence and severity of RP\u003csup\u003e\u003cspan additionalcitationids=\"CR32\" citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e\u003c/sup\u003e. Therefore, breast cancer patients who received extra RNI have a significantly higher rate of RP than those who received whole breast radiotherapy alone\u003csup\u003e\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e,\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e\u003c/sup\u003e. In this study, V500cGy (from 53.3\u0026thinsp;\u0026plusmn;\u0026thinsp;3.0% to 48.3\u0026thinsp;\u0026plusmn;\u0026thinsp;2.9%, p\u0026thinsp;\u0026lt;\u0026thinsp;0.05), V2000cGy (from 25.7\u0026thinsp;\u0026plusmn;\u0026thinsp;1.9% to 20.6\u0026thinsp;\u0026plusmn;\u0026thinsp;3.2%, p\u0026thinsp;\u0026lt;\u0026thinsp;0.05), V3000cGy (from18.3\u0026thinsp;\u0026plusmn;\u0026thinsp;2.5% to 15.3\u0026thinsp;\u0026plusmn;\u0026thinsp;2.3%, p\u0026thinsp;\u0026lt;\u0026thinsp;0.05), and mean dose (from 1332.1\u0026thinsp;\u0026plusmn;\u0026thinsp;128.7cGy to 1165.4\u0026thinsp;\u0026plusmn;\u0026thinsp;148cGy, p\u0026thinsp;\u0026lt;\u0026thinsp;0.05) were decreased to different degrees. The V3000cGy of the ipsilateral lung decreased to less than 20% in all patients. The results of this study further proves the feasibility and necessity of using DIBH to reduce pulmonary exposure during RNI-containing right breast radiotherapy.\u003c/p\u003e \u003cp\u003eAmong the OARs involved in this study, liver changed the most in terms of mean dose (916.9\u0026thinsp;\u0026plusmn;\u0026thinsp;318. 9cGy to 281.2\u0026thinsp;\u0026plusmn;\u0026thinsp;150.3 cGy) and average dose reduction rate(69.4%). Although radiation-induced liver toxicity has been widely recognized, the related research in breast cancer radiotherapy is still insufficient. Only a few radiotherapy planning studies have shown that DIBH technique can achieve good liver protection effect in right breast cancer\u003csup\u003e\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e,\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e,\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e\u003c/sup\u003e. In the DIBH state, the increase of lung volume makes the liver deviate from the target volume to the human foot side, which is the direct reason for the significant reduction of liver dose. Although the evidence related to the clinical benefit of liver protection in breast cancer radiotherapy is still short, according to the ALARA principle, DIBH potential benefit value for liver protection of the right breast cancer radiotherapy patients is still positive.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eWith the development of DIBH radiotherapy technology, the repeatability and stability of interfractional and intrafractional breath holding have been widely concerned\u003csup\u003e\u003cspan additionalcitationids=\"CR39 CR40 CR41\" citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e\u003c/sup\u003e. SGRT-based DIBH radiotherapy adopts optical image-guided positioning to improve the setup accuracy before treatment, and to monitor patients' position changes in real time during treatment, which enhances the repeatability and stability of patients' breath-holding and effectively guarantees treatment accuracy for patients\u003csup\u003e\u003cspan additionalcitationids=\"CR41 CR42\" citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e\u003c/sup\u003e. Amid the implementation of SGRT-based DIBH radiotherapy, the position of the respiratory gating primary point can be manual placed. In most of the reported studies, the position of the gating primary point is not clear, and there is a lack of relevant comparative studies to guide the set up of the gating primary point\u003csup\u003e14,15,43\u0026minus;45\u003c/sup\u003e. AAPM Task Group Report 302 believes that a better respiratory curve can be obtained when the gating point is placed at the xiphoid process\u003csup\u003e\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e\u003c/sup\u003e. D.Reit Z et al\u003csup\u003e\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e\u003c/sup\u003e analysed the breath-hold stability and repeatability of 6013 DIBH fractional treatment. In that study, all patients' gating primary points were placed at the edge of xiphoid process, and the breath-hold amplitude displayed by the SGRT system between patients' fractional treatment was used as an indicator to judge the breath-hold stability and repeatability. Sch\u0026ouml;necker et al\u003csup\u003e\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e\u003c/sup\u003e reported that DIBH radiotherapy for left breast cancer has also been performed by setting gating primary points on the sternum. Among the 31 patients included in this study, the gating primary points of the patients undergoing breast-conserving surgery were placed on the edge of xiphoid process (11 cases) or the middle of sternum (12 cases), and 8 cases of the patients undergoing radical mastectomy surgery were set on the contralateral breast wall where the bolus was avoided. The research team compared and analysed the CBCT validation data collected from 187 fractions in 31 patients under DIBH after dividing them into three groups (EXP group, SM group, LBW group), and performed a retrospective evaluation study on the treatment accuracy.\u003c/p\u003e \u003cp\u003eThe statistical results of the three sets of data showed that, in the SM group and LBW group, the overall setup errors in all directions were 2.4\u0026thinsp;\u0026plusmn;\u0026thinsp;3.0mm and 2.5\u0026thinsp;\u0026plusmn;\u0026thinsp;3.2mm, respectively. The incidence of absolute setup errors within 3mm was 64.1% and 59.8%, respectively and meanwhile, only one fraction showed setup error greater than 8mm in both groups, with an occurrence rate of less than 1%. This indicated that the SM group and LBW group had better breath-hold repeatability and stability, and in turn higher treatment accuracy. Whereas, in EXP group, the overall setup error in all directions was 3.2\u0026thinsp;\u0026plusmn;\u0026thinsp;4.0mm, the incidence of the absolute value of setup error within 3mm was 52.6% and 6 fractions showed abnormal setup error greater than 8mm, five of them clustered in AP direction. Through the analysis of these abnormal data on CBCT images, it was found that inspiratory capacity seriously insufficient occured in 4 patients, and the positions of heart, lung and liver were significantly inconsistent with those of localization CT images, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e.This is an important finding, and although all patients were trained to perform thoracic breathing and were performed CBCT scans while holding their breath to a preset range of gating windows, abnormal breath-hold stability and repeatability persisted.\u003c/p\u003e \u003cp\u003eAfter analysis, the research team believes that the rise in respiration at the edge of xiphoid process is affected by both the amplitude of thoracic and abdominal respiration, and during the course of treatment, patients involuntarily adopt abdominal or mixed breathing to make the breathing amplitude reach the preset range of the gating window, which leads to the relatively poor treatment accuracy of EXP group in this study. For patients with thoracic breathing, the gating point placed on the sternum or breast wall has better interfractions breath-holding repeatability and stability, and the EXP gating point needs to be carefully selected. DIBH radiotherapy for right breast cancer has high overall treatment accuracy under the premise of selecting appropriate gating point location. The analysis of regional anatomical location accuracy is not studied in this paper, which will be concerned in subsequent studies. Theoretically, the location selection of gating points is equally important to ensure the accuracy of DIBH radiotherapy for left and right breast cancer. If conditions permit, abdominal pressure technique can be used in thoracic breathing to control the occurrence of abdominal breathing.\u003c/p\u003e \u003cp\u003eIn addition, we observed large differences in DIBH height when different gating points were placed. Statistics showed that the DIBH heights of the EXP, SM and LBM groups were 13.5\u0026thinsp;\u0026plusmn;\u0026thinsp;3.7mm, 10.3\u0026thinsp;\u0026plusmn;\u0026thinsp;2.4mm, and 9.6\u0026thinsp;\u0026plusmn;\u0026thinsp;2.8mm, respectively and the difference was statistically significant (P\u0026thinsp;\u0026lt;\u0026thinsp;0.05). The corresponding right lung volume increment was 71.3%, 69.9%, and 67.2%, respectively(P\u0026thinsp;=\u0026thinsp;0.08), without statistically significant difference. Although the breath-hold height of EXP group was significantly higher than that of the other two groups, the lung volume increase rate was larger in all three groups without significant difference. Oonsiri et al\u003csup\u003e\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e\u003c/sup\u003e studied the correlation between total lung volume (TLV), central lung distance (CLD), chest wall separation (CWS) and DIBH radiotherapy exclusion criteria for left breast cancer, and found that there was a deterministic relationship between TLV increment and cardiopulmonary dose decrease. The mean increase in lung volume in that study was 41.5%, which can be used as an exclusion criterion for DIBH radiotherapy. In traditional DIBH breathing training, the rise height of the gating point after breathing is generally considered as an important indicator for predicting lung volume increase. Schr\u0026ouml;de et al\u003csup\u003e\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e\u003c/sup\u003e did not specify the position of the gating point during the clinical workflow of DIBH, but required that the rise height of the DIBH gating point be greater than 12m from the baseline. In this study, in the SM group and LBW group with better breath-holding repeatability and stability, a total of 11 patients did not reach 12mm in respiration height, the lowest of which was only 6.5mm, and the right lung volume increment of the patients was above 50%, which was higher than that in Oonsiri\u003csup\u003e\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e\u003c/sup\u003e and other studies. Retrospective planning data in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e also confirmed dosimetric benefits of varying degrees in these patients. We believes that the body surface rise of patients after DIBH varies greatly with different patients and different gating points. If breath-hold height is used as a reference index to evaluate lung volume increment and furthermore emerges as the exclusion criterion for DIBH radiotherapy, it is necessary to further study and clarify the specific reference values corresponding to different gating point locations. Until then, it is still recommended to observe the anatomical position changes and calculate the lung volume increment by scanning FB and DIBH CT images for accurate determination.\u003c/p\u003e \u003cp\u003eThe results of previous radiotherapy planning studies suggested that patients receiving right breast radiotherapy with RNI had significant benefit in heart and lung dosimetry, while patients receiving right breast radiotherapy without RNI had less benefit\u003csup\u003e\u003cspan additionalcitationids=\"CR23 CR24 CR25\" citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e\u003c/sup\u003e. To this end, DIBH radiotherapy was only applied to right breast cancer with RNI for this retrospective study. The results of this study confirmed the restricted effect of DIBH radiotherapy supported by optical surface images on OARs dose(especially liver) and proved that, DIBH technique had high therapeutic accuracy in right breast cancer. In the future, DIBH radiotherapy in right breast cancer without RNI will be studied, so as to explore its broader clinical application value.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eAlthough DIBH radiotherapy has rarely been reported in right-sided breast cancer, a small number of radiotherapy planning studies have shown its potential benefits, especially in right-sided breast cancer patients with RNI. This study based on real treatment data performed retrospective analysis, which reckoned that on the premise of reasonable technology, SGRT-based DIBH technique could better protect patients' hearts, lungs and livers after its application to RNI-containing right breast cancer and interfractions/intrafractions had high repeatability and stability to ensure high precision, which is suggested to be popularized.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003edeep inspiration breath hold (DIBH); regional nodal radiation (RNI); surface guided radiotherapy (SGRT); Free breath (FB); organs at risk (OARs); edge of xiphoid process (EXP); sternum middle (SM); left breast wall (LBW);\u003c/p\u003e\n\u003cp\u003econe beam CT (CBCT); gross tumor volume (GTV); clinical target volume (CTV);\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe study was conducted in accordance with the Declaration of Helsinki, and approved by the Ethics Committee of Zhejiang hospital (protocol code 2022(105k) and date of 26,09,2022).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe data presented in this study are available on request from the corresponding author. The data are not publicly available due to patients, privacy.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no conflict of interest.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was supported in part by the Zhejiang Public Welfare Research Program under Grant LGF20H160020, and in part by the Zhejiang Medical and Health Science and Technology Project under Grant 2022PY078.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors' contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eConceptualization, Jianjun Lai and Haili Hu; methodology, Lu Jiang; data analysis, Jing Wu, Lan Lei and Chuanfeng Zhang; writing\u0026mdash;original draft preparation, Jianjun Lai ; writing\u0026mdash;review and editing, Zhao Jing and Zhibing Wu; supervision, Li qu; All authors have read and agreed to the published version of the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eLei S, Zheng R, Zhang S. \u003cb\u003eet al\u003c/b\u003e. 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RADIOTHER ONCOL. 2016;119:831.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAl-Hallaq HA, Cervi\u0026ntilde;o L, Gutierrez AN. \u003cb\u003eet al\u003c/b\u003e. AAPM task group report 302:Surface-guided radiotherapy. MED PHYS. 2022;49:e82\u0026ndash;112.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eReitz D, Walter F, Sch\u0026ouml;necker S. \u003cb\u003eet al\u003c/b\u003e. Stability and reproducibility of 6013 deep inspiration breath-holds in left-sided breast Cancer. Radiat Oncol. 2020;15:121.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSch\u0026ouml;necker F, Walter P, Freislederer C. \u003cb\u003eet al\u003c/b\u003e. \u003cb\u003eTreatment planning and evaluation of gated radiotherapy in left-sided breast cancer patients using the Catalyst\u003c/b\u003e\u003csup\u003e\u003cb\u003eTM\u003c/b\u003e\u003c/sup\u003e\u003cb\u003e/Sentinel\u0026trade; system for deep inspiration breath-hold (DIBH)\u003c/b\u003e. Radiat Oncol. 2016;11:143\u0026ndash;53.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSchr\u0026ouml;der C, Kirschke S, Blank E. \u003cb\u003eet al\u003c/b\u003e. Deep inspiration breath-hold for patients with left-sided breast cancer-A one-fits-all approach? A prospective analysis of patient selection using dosimetrical and practical aspects. Br J Radiol. 2022;95:20210295.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDell'Oro M, Giles E, Sharkey A. \u003cb\u003eet al\u003c/b\u003e. A Retrospective Dosimetric Study of Radiotherapy Patients with Left-Sided Breast Cancer; Patient Selection Criteria for Deep Inspiration Breath Hold Technique. Cancers (Basel). 2019;11:259.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Right-sided breast cancer, Radiotherapy, DIBH, SGRT","lastPublishedDoi":"10.21203/rs.3.rs-2185678/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-2185678/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eBackground:\u003c/strong\u003e This paper studied retrospectively the dosimetry and therapeutic accuracy of deep inspiration breath hold (DIBH) radiotherapy in regional nodal radiation (RNI)-containing right-sided breast cancer patients who had completed treatment based on surface guided radiotherapy (SGRT) technology, hoping to clarify the clinical application value and related issues .\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMethods:\u003c/strong\u003e Free breath (FB) and DIBH plans were prepared for31 RNI-containing right breast cancer patients who had completed DIBH radiotherapy based on SGRT technology. Four organs at risk (OARs) including heart, right coronary artery (RCA), right lung and liver were made dosimetriccomparison on the premise that the planning target volume was met dose-volume prescription requirements. Meanwhile, 31 patients were divided into edge of xiphoid process (EXP), sternum middle (SM)and left breast wall (LBW) groups according to different positions of respiratory gating primary points. The CBCT setup error data of the three groups were contrasted for the treatment accuracy study, and the effects of different gating window heights on the lung volume increment of the right side were compared among the three groups.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults: \u003c/strong\u003eAll planning target volume met the dose-volume coverage criteria. Compared with FB, DIBH slumpedthe maximum dose of heart and RCA by 44.3% and 46.7% respectively. The mean dose was went down by 12.5% for right lung. The mean liver dosedecreased the most, with an average reduction rate of 69.4%. The setup error of EXP group in the anterior-posterior (AP) direction was 3.6±4.5mm, significantly higher than the other two groups (2.2±2.6mm, 2.4±3.1mm). The rightlung volume increment in EXP, SM and LBW groups was 72.3%, 69.9 % and 67.2%, respectively(P=0.08), and the corresponding breath-holding heights were 13.5±3.7mm, 10.3±2.4mm, and 9.6±2.8mm, respectively(p\u0026lt;0.05).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusions: \u003c/strong\u003eSGRT-based DIBH can better protect the heart, RCA, ipsilateral lung and liver of right breast cancer patients combined with RNI. Different respiratory gating primary points have different therapeutic accuracy and breath-hold height. On the premise of reasonable respiratory gating primary points, interfractions can be widely applied as it has high repeatability and breath-holding stability to ensure therapeutic accuracy.\u003c/p\u003e","manuscriptTitle":"SGRT-based DIBH radiotherapy practice for right breast cancer combined with RNI: A retrospective study on dosimetry and treatment accuracy","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2022-10-25 15:40:17","doi":"10.21203/rs.3.rs-2185678/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"3694fe80-f9d7-451a-af58-7611ba152cad","owner":[],"postedDate":"October 25th, 2022","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2022-12-04T21:59:20+00:00","versionOfRecord":[],"versionCreatedAt":"2022-10-25 15:40:17","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-2185678","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-2185678","identity":"rs-2185678","version":["v1"]},"buildId":"cTy_lsJlmDsVRNrSptgXS","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}