FLARE Study – Fluorescence-guided Lymphadenectomy for augmented retrieval and Evaluation in Rectal Cancer surgery

FLARE Study – Fluorescence-guided Lymphadenectomy for augmented retrieval and Evaluation in Rectal Cancer surgery | 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 Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article FLARE Study – Fluorescence-guided Lymphadenectomy for augmented retrieval and Evaluation in Rectal Cancer surgery Nishtha ., Syed Altaf, Pavan Sugoor This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7164691/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 : In patients with mid-to-lower rectal cancer undergoing neoadjuvant chemoradiotherapy (NACRT), lymph node (LN) retrieval is often suboptimal, affecting accurate staging and prognosis. Fluorescence-guided surgery (FGS) using Indocyanine Green (ICG) has emerged as a technique to enhance lymphatic mapping and identify aberrant lymph nodes (LNs) that may be missed while operating under conventional white light. Objective: To assess whether peri-tumoral tattooing with ICG and FGS alters the extent of lymphadenectomy and improves LN yield in rectal cancer patients post-NACRT. Methods: This investigator-initiated, quasi-experimental study utilized a prospectively maintained database from January 2023 to December 2024. Following 1:1 propensity score matching for eight variables (age, gender, BMI, tumor location, T-stage, N-stage, surgical procedure, and tattooing), 46 ICG-tattooed patients were compared to 46 controls. The primary outcome was the number of patients in whom FGS modified the extent of lymphadenectomy. Secondary outcomes included the number and positivity of aberrant LNs, and their size. Results: Median aberrant LNs identified was 2 per patient. The LN yield was significantly higher in the tattooed group (14 ± 3.7) than in the non-tattooed group (7 ± 3, P < 0.001). In 23 patients (50%), FGS altered the lymphadenectomy extent. Five aberrant nodes (10.87%) were malignant, located in stations 16B1, 16B2, and mesorectal sub-zones. The mean size of aberrant nodes was 4 ± 2 mm. Conclusion: Fluorescence-guided lymphadenectomy significantly improves LN yield and aids in detecting small, otherwise occult, aberrant lymph nodes. ICG-guided techniques should be considered an adjunct to standard rectal cancer surgery following NACRT to ensure optimal oncologic outcomes. Introduction Accurate lymph node (LN) staging is a cornerstone in the management of rectal cancer, impacting decisions about adjuvant treatment and prognostication. Guidelines from the American Joint Committee on Cancer (AJCC) and the National Comprehensive Cancer Network (NCCN) recommend retrieving at least 12 lymph nodes to ensure reliable staging and to avoid under staging that may result in stage migration [1,2]. However, this target is often not met in patients who undergo neoadjuvant chemoradiotherapy (NACRT), due to therapy-induced lymphoid atrophy and stromal fibrosis [3, 4]. The implications of inadequate nodal harvest extend beyond staging accuracy. Several studies have demonstrated that a higher number of LNs retrieved is associated with improved overall survival, possibly due to more accurate detection of micrometastasis and subsequent tailoring of adjuvant therapy [5,6]. Indocyanine green (ICG) fluorescence-guided surgery (FGS) has emerged as a novel technique for real-time visualization of lymphatic architecture. The use of ICG in colorectal surgery has shown promise in enhancing nodal detection, improving lymphadenectomy quality, and localizing small aberrant nodes that may be missed during standard dissection [7–9]. Fluorescence-guided surgery (FGS), using Indocyanine Green (ICG), has demonstrated promise in sentinel LN mapping and lymphatic visualization in gastrointestinal malignancies [10]. Its role in improving the nodal harvest, particularly in challenging post-NACRT rectal cancer cases, remains under-explored. Given these challenges and opportunities, our study investigates whether peri-tumoral ICG tattooing and fluorescence-guided lymphadenectomy can enhance LN yield, improve LN retrieval and modify lymphadenectomy extent by identifying aberrant lymphatic drainage, thus affecting intraoperative decision-making in rectal cancer patients post-NACRT. Methodology Study Design This was an investigator-initiated, single-center, quasi-experimental study conducted at the Department of Surgical Oncology, Kidwai Memorial Institute of Oncology, Bengaluru, India. The study was conducted in accordance with the ethical principles laid down in the Declaration of Helsinki. Written informed consent was obtained from all patients undergoing fluorescence-guided surgery (FGS). Patient Selection A total of 278 patients with biopsy-proven rectal adenocarcinoma treated between January 2023 and December 2024 were screened. Patients with tumors located in the mid to lower rectum and who had completed standard neoadjuvant chemoradiotherapy (NACRT) were eligible for inclusion. NACRT consisted of long-course radiotherapy (50.4 Gy in 28 fractions) combined with concurrent 5-fluorouracil or capecitabine-based chemotherapy. Exclusion criteria included: Tumors located in the upper third of the rectum Treatment-naïve rectal cancers Known hypersensitivity or contraindication to Indocyanine Green (ICG) History of previous pelvic surgery or radiation Propensity Score Matching Of the 278 eligible patients, 46 who underwent FGS with peri-tumoral ICG injection were identified. To minimize selection bias, 1:1 propensity score matching was performed using a logistic regression model based on eight preoperative variables: age, gender, body mass index (BMI), tumor location, clinical T stage, clinical N stage, surgical procedure (LAR, APR, or Hartmann's), and ICG tattooing. A total of 46 non-tattooed patients were selected to match the fluorescence group, forming two well-balanced cohorts (n = 46 each). ICG Tattooing Procedure ICG was reconstituted to a concentration of 2.5 mg/mL. A total of 1 mL was injected peri-tumoral into two quadrants of the rectal wall during preoperative flexible sigmoidoscopy or proctoscopy. The injection was performed into the submucosal plane using a standard endoscopic injection or spinal needle under direct visualization, after patient was under general anaesthesia. Surgical Technique All patients underwent total mesorectal excision (TME) under general anesthesia by experienced colorectal surgeons. Standard oncological principles were followed, including high ligation of the inferior mesenteric artery (IMA), sharp mesorectal dissection, and resection with appropriate distal and radial margins. In the tattooed group, near-infrared fluorescence (NIRF) imaging was used intraoperatively via a laparoscopic camera system equipped with a NIR mode (Stryker 1688). Fluorescent lymphatic channels and nodes were visualized after mobilization of the rectum and mesorectum. The extent of lymphadenectomy was extended in cases where fluorescence identified aberrant lymphatic drainage outside standard TME fields. Pathological Evaluation Resected specimens were submitted fresh to pathology. Mesorectal fat was palpated and dissected manually by two experienced surgical pathologists. ICG fluorescence-enhanced nodes were identified grossly and by palpation, then processed as per standard protocols. Lymph nodes were counted and examined histologically using hematoxylin and eosin staining. Node positivity was defined by presence of tumor cells on microscopy. Outcome Measures Primary Outcome: The proportion of patients in whom FGS altered the intraoperative extent of lymphadenectomy. Secondary Outcomes: Number of lymph nodes retrieved Number and location of aberrant lymph nodes detected via fluorescence Histopathological positivity of aberrant nodes Size of aberrant lymph nodes (as measured microscopically) Statistical Analysis Continuous variables were expressed as means ± standard deviation (SD) or medians with interquartile range (IQR), depending on distribution. Categorical variables were expressed as counts and percentages. The Mann-Whitney U test was used for nonparametric data, while the Chi-square or Fisher’s exact test was used for categorical variables. A p-value < 0.05 was considered statistically significant. Propensity score matching was performed using a nearest-neighbor algorithm without replacement, with a caliper width of 0.1. All analyses were conducted using R statistical software version 4.3.1 and SPSS version 26.0 Results Post-matching analysis included 46 patients in each group Table 1, 2. LN yield was significantly higher in the tattooed group (14 ± 3.7) compared to the non-tattooed group (7 ± 3, P < 0.001). Median aberrant LNs identified per patient was 2. FGS altered the surgical plan in 23 (50%) patients. Five aberrant nodes (10.87%) were histologically malignant (in stations 16B1, 16B2, and mesorectal zones). Mean aberrant node size was 4 ± 2 mm. No ICG-related complications or increased morbidity were observed. Table 1 Demographic characteristics Parameter Subset Non- tattoo group (46) Tattoo group (46) Univariate Analysis Multivariate Analysis Age 31-40 year 41-50 year 51- 60 year 61-70 year 71-80 year 08 (17.4 %) 11 (23.9 %) 12 (26.1 %) 09 (18.5 %) 06 (14.1 %) 08 11 12 09 06 0.005 0.173 0.555 0.668 0.030 0.125 0.796 0.898 Gender Male Female 24 (52.2 %) 22 (47.8 %) 24 22 0.24 - BMI 25 03 (6.5 %) 18 (39.1 %) 21 (45.7 %) 04 (8.7 %) 03 18 21 04 0.032 0.039 0.167 0.001 0.052 0.188 Location Mid third Lower third 27 (58.7 %) 19 (41.3 %) 27 19 0.729 - Table 2 Tumor Charactersitcs Parameter Subset Non- tattoo group (46) Tattoo group (46) Univariate Analysis Multivariate Analysis T stage T3a/b T3c/d T4 10 (21.7 %) 26 (56.5 %) 10 (21.7 %) 10 26 10 0.281 0.764 - N stage N0 N1 N2 07 (15.2 %) 16 (34.8 %) 23 (50 %) 07 16 23 0.001 0.024 0.029 Grade Grade I Grade II Grade III 11 (23.9 %) 18 (39.1 %) 17 (37 %) 11 20 15 0.562 0.903 - Surgery ULAR APR 26 (56.5 %) 20 (43.4 %) 27 19 0.635 - Discussion Previous studies have suggested that inadequate LN retrieval post-NACRT may underestimate nodal staging [ 3 , 6 ]. Our study however demonstrates that fluorescence-guided lymphadenectomy using peri-tumoral ICG tattooing significantly increases lymph node yield and facilitates the identification of aberrant nodes in rectal cancer patients post-NACRT. The LN yield was nearly doubled compared to the non-tattooed group, supporting the feasibility and utility of this method in challenging surgical fields affected by radiotherapy-induced fibrosis. These findings are consistent with previous reports suggesting that ICG helps in sentinel and non-sentinel lymph node mapping. Bartels et al. and Kang et al. reported improved nodal harvest and accuracy of staging in colorectal cancer patients when ICG tattooing was used preoperatively [ 7 , 9 ]. Importantly, our study revealed that in 50% of patients, fluorescence imaging led to modification of the planned lymphadenectomy, uncovering aberrant lymphatic drainage pathways. This highlights the real-time surgical advantage of ICG over conventional techniques, which rely solely on anatomical landmarks. Aberrant nodes—often small (< 5 mm) and outside the standard TME field—were pathologically malignant in over 10% of cases. Such nodes are likely to be missed using standard approaches, leading to under-staging and suboptimal adjuvant therapy. Similar observations have been made in sentinel node mapping literature, where carbon or ICG uptake enhances intraoperative detection and pathological yield [ 11 , 12 ]. Our results also align with the concept of the “Will Rogers phenomenon” where stage migration due to better detection tools (in this case, ICG-FGS) could translate into improved survival by appropriately upstaging patients who would otherwise be considered node-negative [ 13 ]. Limitations of this study include its single-center design, relatively small sample size, and absence of long-term oncologic outcomes. However, the use of rigorous propensity score matching reduces selection bias and strengthens internal validity. Future multicenter randomized trials are warranted to confirm the oncologic benefits and cost-effectiveness of incorporating FGS into standard practice, particularly in low-resource settings where ICG is becoming more accessible. Conclusion Peri-tumoral ICG tattooing and fluorescence-guided lymphadenectomy significantly enhance lymph node yield in rectal cancer post-NACRT. This technique improves intraoperative visualization of aberrant nodes, ensuring better oncologic outcomes and staging accuracy. It should be considered as a standard adjunct in eligible rectal cancer surgeries. Declarations Funding Declaration: None Data Availability: The de-identified datasets generated and analyzed during the current study are available and shall be shared if necessary. Conflict of interest: None Competing Interest declaration: None Email address of corresponding author: [email protected] Author Contribution N: Conceptualization, writing of manuscript, preparing visual abstract, review of manuscriptP.S: Conceptualization, review of manuscript, SupervisionS.A: Review of manuscript, Supervision Acknowledgement Tanmay Gumbar References Chang GJ, Rodriguez-Bigas MA, Skibber JM, Moyer VA. Lymph node evaluation and survival after curative resection of colon cancer: systematic review. J Natl Cancer Inst . 2007;99(6):433–41. Edge SB, Compton CC. The 7th edition of the AJCC cancer staging manual. Ann Surg Oncol . 2010;17(6):1471–4. Ha YH, et al. Influence of preoperative chemoradiotherapy on the number of lymph nodes retrieved in rectal cancer. Ann Surg . 2010;252(2):336–40. Wang H, et al. Patterns of lymph node metastasis differ in colon and rectal carcinomas. World J Gastroenterol . 2010;16(43):5375–9. Le Voyer TE, et al. Colon cancer survival is associated with increasing number of lymph nodes analyzed. J Clin Oncol . 2003;21(3):2912–9. Swanson RS, et al. Prognosis of T3N0 colon cancer is dependent on the number of lymph nodes examined. Ann Surg Oncol . 2003;10(1):65–71. Bartels SA, et al. The effect of colonoscopic tattooing on lymph node retrieval. Gastrointest Endosc . 2012;76(4):793–800. Cho YB, et al. Tumor localization for laparoscopic colorectal surgery. World J Surg . 2007;31(7):1491–5. Kang J, et al. Effect of preoperative colonoscopic tattooing on lymph node harvest in T1 colorectal cancer. Int J Colorectal Dis . 2015;30(10):1349–55. Boni L, David G, Mangano A, et al. Clinical applications of indocyanine green (ICG) enhanced fluorescence in laparoscopic surgery. Surg Endosc. 2015;29(7):2046-2055. Spatz H, et al. Sentinel lymph node mapping as a side-effect of colonoscopic tattooing. Surg Endosc . 2010;24(3):589–93. Dawson K, et al. Preoperative tattooing and improved lymph node retrieval rates. Arch Surg . 2010;145(9):826–30. Feinstein AR, et al. The Will Rogers phenomenon: stage migration and new diagnostic techniques. N Engl J Med . 1985;312(25):1604–8. Additional Declarations No competing interests reported. Supplementary Files FLAREvisualabstract.jpeg Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board 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-7164691","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":494124437,"identity":"ca2edf89-d81c-40d8-aab0-0898259bff8c","order_by":0,"name":"Nishtha .","email":"","orcid":"","institution":"Kidwai Memorial Institute of Oncology","correspondingAuthor":false,"prefix":"","firstName":"Nishtha","middleName":"","lastName":".","suffix":""},{"id":494124439,"identity":"bf065bf8-d2d4-469a-8019-80f8c311d5fc","order_by":1,"name":"Syed Altaf","email":"","orcid":"","institution":"Kidwai Memorial Institute of Oncology","correspondingAuthor":false,"prefix":"","firstName":"Syed","middleName":"","lastName":"Altaf","suffix":""},{"id":494124442,"identity":"b4b462ed-6cd4-4830-988a-e60ebdccddb8","order_by":2,"name":"Pavan Sugoor","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA+ElEQVRIiWNgGAWjYJADxgcfKoAUM3MD0VqYDWecAVGMxGthk+ZsA9uGX4s5+xnDzwV/Dtv1s/c+kGacVxvN3w7U8qNiG04tlj05xtIz2w4nz+w5bmBcuO147ozDjA2MPWdu49RicCAtQZq34XCywY00huSZ247lNgC1MDO24dFy/lnyb54/EC2Heeccy51PUMuN5GPSPGyH7YBaGJt5G2pyNxDSYjnj8TFr3rb0BMmeY8yMM44dyN0I1HIQn1/M+RObb/P8sbbnZ29j//Ghpi533vnDBx/8qMDjMCid2AChD4PJAzjVI2mxh9J1+BSPglEwCkbBCAUA+Ald9tnPncAAAAAASUVORK5CYII=","orcid":"","institution":"Kidwai Memorial Institute of Oncology","correspondingAuthor":true,"prefix":"","firstName":"Pavan","middleName":"","lastName":"Sugoor","suffix":""}],"badges":[],"createdAt":"2025-07-19 13:23:13","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7164691/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7164691/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":109762212,"identity":"b52e4875-434f-40f8-b64b-4a5908cf948e","added_by":"auto","created_at":"2026-05-22 07:30:57","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":177271,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7164691/v1/57bc206d-5160-4922-a948-6f5de45dbb0d.pdf"},{"id":88252556,"identity":"75dde827-9007-4ec6-87a8-fcf1bead4021","added_by":"auto","created_at":"2025-08-04 13:50:26","extension":"jpeg","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":377718,"visible":true,"origin":"","legend":"","description":"","filename":"FLAREvisualabstract.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7164691/v1/0aa9dce6ade2db12321f1d4b.jpeg"}],"financialInterests":"No competing interests reported.","formattedTitle":"FLARE Study – Fluorescence-guided Lymphadenectomy for augmented retrieval and Evaluation in Rectal Cancer surgery","fulltext":[{"header":"Introduction","content":"\u003cp\u003eAccurate lymph node (LN) staging is a cornerstone in the management of rectal cancer, impacting decisions about adjuvant treatment and prognostication. Guidelines from the American Joint Committee on Cancer (AJCC) and the National Comprehensive Cancer Network (NCCN) recommend retrieving at least 12 lymph nodes to ensure reliable staging and to avoid under staging that may result in stage migration [1,2]. However, this target is often not met in patients who undergo neoadjuvant chemoradiotherapy (NACRT), due to therapy-induced lymphoid atrophy and stromal fibrosis [3, 4].\u003c/p\u003e\n\u003cp\u003eThe implications of inadequate nodal harvest extend beyond staging accuracy. Several studies have demonstrated that a higher number of LNs retrieved is associated with improved overall survival, possibly due to more accurate detection of micrometastasis and subsequent tailoring of adjuvant therapy [5,6].\u003c/p\u003e\n\u003cp\u003eIndocyanine green (ICG) fluorescence-guided surgery (FGS) has emerged as a novel technique for real-time visualization of lymphatic architecture. The use of ICG in colorectal surgery has shown promise in enhancing nodal detection, improving lymphadenectomy quality, and localizing small aberrant nodes that may be missed during standard dissection [7\u0026ndash;9].\u003c/p\u003e\n\u003cp\u003eFluorescence-guided surgery (FGS), using Indocyanine Green (ICG), has demonstrated promise in sentinel LN mapping and lymphatic visualization in gastrointestinal malignancies [10]. Its role in improving the nodal harvest, particularly in challenging post-NACRT rectal cancer cases, remains under-explored.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eGiven these challenges and opportunities, our study investigates whether peri-tumoral ICG tattooing and fluorescence-guided lymphadenectomy can enhance LN yield, improve LN retrieval and modify lymphadenectomy extent by identifying aberrant lymphatic drainage, thus affecting intraoperative decision-making in rectal cancer patients post-NACRT.\u003cbr\u003e\u0026nbsp;\u003c/p\u003e"},{"header":"Methodology","content":"\u003cp\u003e\u003cstrong\u003eStudy Design\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis was an investigator-initiated, single-center, quasi-experimental study conducted at the Department of Surgical Oncology, Kidwai Memorial Institute of Oncology, Bengaluru, India. The study was conducted in accordance with the ethical principles laid down in the Declaration of Helsinki. Written informed consent was obtained from all patients undergoing fluorescence-guided surgery (FGS).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePatient Selection\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA total of 278 patients with biopsy-proven rectal adenocarcinoma treated between January 2023 and December 2024 were screened. Patients with tumors located in the mid to lower rectum and who had completed standard neoadjuvant chemoradiotherapy (NACRT) were eligible for inclusion. NACRT consisted of long-course radiotherapy (50.4 Gy in 28 fractions) combined with concurrent 5-fluorouracil or capecitabine-based chemotherapy.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eExclusion criteria included:\u003c/strong\u003e\u003c/p\u003e\n\u003cul type=\"disc\"\u003e\n \u003cli\u003eTumors located in the upper third of the rectum\u003c/li\u003e\n \u003cli\u003eTreatment-na\u0026iuml;ve rectal cancers\u003c/li\u003e\n \u003cli\u003eKnown hypersensitivity or contraindication to Indocyanine Green (ICG)\u003c/li\u003e\n \u003cli\u003eHistory of previous pelvic surgery or radiation\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003e\u003cstrong\u003ePropensity Score Matching\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eOf the 278 eligible patients, 46 who underwent FGS with peri-tumoral ICG injection were identified. To minimize selection bias, 1:1 propensity score matching was performed using a logistic regression model based on eight preoperative variables: age, gender, body mass index (BMI), tumor location, clinical T stage, clinical N stage, surgical procedure (LAR, APR, or Hartmann\u0026apos;s), and ICG tattooing. A total of 46 non-tattooed patients were selected to match the fluorescence group, forming two well-balanced cohorts (n = 46 each).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eICG Tattooing Procedure\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eICG was reconstituted to a concentration of 2.5 mg/mL. A total of 1 mL was injected peri-tumoral into two quadrants of the rectal wall during preoperative flexible sigmoidoscopy or proctoscopy. The injection was performed into the submucosal plane using a standard endoscopic injection or spinal needle under direct visualization, after patient was under general anaesthesia.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSurgical Technique\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll patients underwent \u0026nbsp;total mesorectal excision (TME) under general anesthesia by experienced colorectal surgeons. Standard oncological principles were followed, including high ligation of the inferior mesenteric artery (IMA), sharp mesorectal dissection, and resection with appropriate distal and radial margins.\u003c/p\u003e\n\u003cp\u003eIn the tattooed group, near-infrared fluorescence (NIRF) imaging was used intraoperatively via a laparoscopic camera system equipped with a NIR mode (Stryker 1688). Fluorescent lymphatic channels and nodes were visualized after mobilization of the rectum and mesorectum. The extent of lymphadenectomy was extended in cases where fluorescence identified aberrant lymphatic drainage outside standard TME fields.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePathological Evaluation\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eResected specimens were submitted fresh to pathology. Mesorectal fat was palpated and dissected manually by two experienced surgical pathologists. ICG fluorescence-enhanced nodes were identified grossly and by palpation, then processed as per standard protocols. Lymph nodes were counted and examined histologically using hematoxylin and eosin staining. Node positivity was defined by presence of tumor cells on microscopy.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eOutcome Measures\u003c/strong\u003e\u003c/p\u003e\n\u003cul type=\"disc\"\u003e\n \u003cli\u003e\u003cstrong\u003ePrimary Outcome:\u003c/strong\u003e The proportion of patients in whom FGS altered the intraoperative extent of lymphadenectomy.\u003c/li\u003e\n \u003cli\u003e\u003cstrong\u003eSecondary Outcomes:\u003c/strong\u003e\n \u003cul type=\"circle\"\u003e\n \u003cli\u003eNumber of lymph nodes retrieved\u003c/li\u003e\n \u003cli\u003eNumber and location of aberrant lymph nodes detected via fluorescence\u003c/li\u003e\n \u003cli\u003eHistopathological positivity of aberrant nodes\u003c/li\u003e\n \u003cli\u003eSize of aberrant lymph nodes (as measured microscopically)\u003c/li\u003e\n \u003c/ul\u003e\n \u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003e\u003cstrong\u003eStatistical Analysis\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eContinuous variables were expressed as means \u0026plusmn; standard deviation (SD) or medians with interquartile range (IQR), depending on distribution. Categorical variables were expressed as counts and percentages. The Mann-Whitney U test was used for nonparametric data, while the Chi-square or Fisher\u0026rsquo;s exact test was used for categorical variables. A p-value \u0026lt; 0.05 was considered statistically significant. Propensity score matching was performed using a nearest-neighbor algorithm without replacement, with a caliper width of 0.1. All analyses were conducted using R statistical software version 4.3.1 and SPSS version 26.0\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003ePost-matching analysis included 46 patients in each group Table 1, 2. LN yield was significantly higher in the tattooed group (14 \u0026plusmn; 3.7) compared to the non-tattooed group (7 \u0026plusmn; 3, P \u0026lt; 0.001). Median aberrant LNs identified per patient was 2. FGS altered the surgical plan in 23 (50%) patients.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;Five aberrant nodes (10.87%) were histologically malignant (in stations 16B1, 16B2, and mesorectal zones). Mean aberrant node size was 4 \u0026plusmn; 2 mm. No ICG-related complications or increased morbidity were observed.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 1 Demographic characteristics\u003c/strong\u003e\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"100%\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 15px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eParameter\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 15px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eSubset\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eNon- tattoo group (46)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 15px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eTattoo group (46)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eUnivariate Analysis \u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 19px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eMultivariate\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003eAnalysis\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 15px;\"\u003e\n \u003cp\u003eAge\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 15px;\"\u003e\n \u003cp\u003e31-40 year\u003c/p\u003e\n \u003cp\u003e41-50 year\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e51- 60 year\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e61-70 year\u003c/p\u003e\n \u003cp\u003e71-80 year\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e08 (17.4 %)\u003c/p\u003e\n \u003cp\u003e11 (23.9 %)\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e12 (26.1 %)\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e09 (18.5 %)\u003c/p\u003e\n \u003cp\u003e06 (14.1 %)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 15px;\"\u003e\n \u003cp\u003e08\u003c/p\u003e\n \u003cp\u003e11\u003c/p\u003e\n \u003cp\u003e12\u003c/p\u003e\n \u003cp\u003e09\u003c/p\u003e\n \u003cp\u003e06\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e0.005\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e0.173\u003c/p\u003e\n \u003cp\u003e0.555\u003c/p\u003e\n \u003cp\u003e0.668\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 19px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e0.030\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e0.125\u003c/p\u003e\n \u003cp\u003e0.796\u003c/p\u003e\n \u003cp\u003e0.898\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 15px;\"\u003e\n \u003cp\u003eGender\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 15px;\"\u003e\n \u003cp\u003eMale\u0026nbsp;\u003c/p\u003e\n \u003cp\u003eFemale\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e24 (52.2 %)\u003c/p\u003e\n \u003cp\u003e22 (47.8 %)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 15px;\"\u003e\n \u003cp\u003e24\u003c/p\u003e\n \u003cp\u003e22\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e0.24\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 19px;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 15px;\"\u003e\n \u003cp\u003eBMI\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 15px;\"\u003e\n \u003cp\u003e\u0026lt;18.5\u003c/p\u003e\n \u003cp\u003e18.5- 22.9\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e23-24.9\u003c/p\u003e\n \u003cp\u003e\u0026gt; 25\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e03 (6.5 %)\u003c/p\u003e\n \u003cp\u003e18 (39.1 %)\u003c/p\u003e\n \u003cp\u003e21 (45.7 %)\u003c/p\u003e\n \u003cp\u003e04 (8.7 %)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 15px;\"\u003e\n \u003cp\u003e03\u003c/p\u003e\n \u003cp\u003e18\u003c/p\u003e\n \u003cp\u003e21\u003c/p\u003e\n \u003cp\u003e04\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e0.032\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e0.039\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e0.167\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 19px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e0.001\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e0.052\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e0.188\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 15px;\"\u003e\n \u003cp\u003eLocation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 15px;\"\u003e\n \u003cp\u003eMid third\u003c/p\u003e\n \u003cp\u003eLower third\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e27 (58.7 %)\u003c/p\u003e\n \u003cp\u003e19 (41.3 %)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 15px;\"\u003e\n \u003cp\u003e27\u003c/p\u003e\n \u003cp\u003e19\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e0.729\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 19px;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 2 Tumor Charactersitcs\u003c/strong\u003e\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"100%\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eParameter\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 14px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eSubset\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 18px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;Non- tattoo group\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003e(46)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eTattoo group\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003e(46)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eUnivariate Analysis\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 18px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eMultivariate Analysis\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003eT stage\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 14px;\"\u003e\n \u003cp\u003eT3a/b\u003c/p\u003e\n \u003cp\u003eT3c/d\u003c/p\u003e\n \u003cp\u003eT4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 18px;\"\u003e\n \u003cp\u003e10 (21.7 %)\u003c/p\u003e\n \u003cp\u003e26 (56.5 %)\u003c/p\u003e\n \u003cp\u003e10 (21.7 %)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e10\u003c/p\u003e\n \u003cp\u003e26\u003c/p\u003e\n \u003cp\u003e10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e0.281\u003c/p\u003e\n \u003cp\u003e0.764\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 18px;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003eN \u0026nbsp;stage\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 14px;\"\u003e\n \u003cp\u003eN0\u003c/p\u003e\n \u003cp\u003eN1\u003c/p\u003e\n \u003cp\u003eN2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 18px;\"\u003e\n \u003cp\u003e07 (15.2 %)\u003c/p\u003e\n \u003cp\u003e16 (34.8 %)\u003c/p\u003e\n \u003cp\u003e23 (50 %)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e07\u003c/p\u003e\n \u003cp\u003e16\u003c/p\u003e\n \u003cp\u003e23\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e0.001\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e0.024\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 18px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e0.029\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003eGrade\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 14px;\"\u003e\n \u003cp\u003eGrade I\u003c/p\u003e\n \u003cp\u003eGrade II\u003c/p\u003e\n \u003cp\u003eGrade III\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 18px;\"\u003e\n \u003cp\u003e11 (23.9 %)\u003c/p\u003e\n \u003cp\u003e18 (39.1 %)\u003c/p\u003e\n \u003cp\u003e17 (37 %)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e11\u003c/p\u003e\n \u003cp\u003e20\u003c/p\u003e\n \u003cp\u003e15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e0.562\u003c/p\u003e\n \u003cp\u003e0.903\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 18px;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003eSurgery\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 14px;\"\u003e\n \u003cp\u003eULAR\u003c/p\u003e\n \u003cp\u003eAPR\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 18px;\"\u003e\n \u003cp\u003e26 (56.5 %)\u003c/p\u003e\n \u003cp\u003e20 (43.4 %)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e27\u003c/p\u003e\n \u003cp\u003e19\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e0.635\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 18px;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e"},{"header":"Discussion","content":"\u003cp\u003ePrevious studies have suggested that inadequate LN retrieval post-NACRT may underestimate nodal staging [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e Our study however demonstrates that fluorescence-guided lymphadenectomy using peri-tumoral ICG tattooing significantly increases lymph node yield and facilitates the identification of aberrant nodes in rectal cancer patients post-NACRT. The LN yield was nearly doubled compared to the non-tattooed group, supporting the feasibility and utility of this method in challenging surgical fields affected by radiotherapy-induced fibrosis.\u003c/p\u003e\u003cp\u003eThese findings are consistent with previous reports suggesting that ICG helps in sentinel and non-sentinel lymph node mapping. Bartels et al. and Kang et al. reported improved nodal harvest and accuracy of staging in colorectal cancer patients when ICG tattooing was used preoperatively [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eImportantly, our study revealed that in 50% of patients, fluorescence imaging led to modification of the planned lymphadenectomy, uncovering aberrant lymphatic drainage pathways. This highlights the real-time surgical advantage of ICG over conventional techniques, which rely solely on anatomical landmarks.\u003c/p\u003e\u003cp\u003eAberrant nodes\u0026mdash;often small (\u0026lt;\u0026thinsp;5 mm) and outside the standard TME field\u0026mdash;were pathologically malignant in over 10% of cases. Such nodes are likely to be missed using standard approaches, leading to under-staging and suboptimal adjuvant therapy. Similar observations have been made in sentinel node mapping literature, where carbon or ICG uptake enhances intraoperative detection and pathological yield [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eOur results also align with the concept of the \u0026ldquo;Will Rogers phenomenon\u0026rdquo; where stage migration due to better detection tools (in this case, ICG-FGS) could translate into improved survival by appropriately upstaging patients who would otherwise be considered node-negative [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eLimitations of this study include its single-center design, relatively small sample size, and absence of long-term oncologic outcomes. However, the use of rigorous propensity score matching reduces selection bias and strengthens internal validity.\u003c/p\u003e\u003cp\u003eFuture multicenter randomized trials are warranted to confirm the oncologic benefits and cost-effectiveness of incorporating FGS into standard practice, particularly in low-resource settings where ICG is becoming more accessible.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003ePeri-tumoral ICG tattooing and fluorescence-guided lymphadenectomy significantly enhance lymph node yield in rectal cancer post-NACRT. This technique improves intraoperative visualization of aberrant nodes, ensuring better oncologic outcomes and staging accuracy. It should be considered as a standard adjunct in eligible rectal cancer surgeries.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eFunding Declaration:\u0026nbsp;\u003c/strong\u003eNone\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData Availability:\u0026nbsp;\u003c/strong\u003eThe de-identified datasets generated and analyzed during the current study are available and shall be shared if necessary.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflict of interest:\u003c/strong\u003e None\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting Interest declaration:\u0026nbsp;\u003c/strong\u003eNone\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEmail address of corresponding author: [email protected]\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor Contribution\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eN: Conceptualization, writing of manuscript, preparing visual abstract, review of manuscriptP.S: Conceptualization, review of manuscript, SupervisionS.A: Review of manuscript, Supervision\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eTanmay Gumbar\u003c/p\u003e"},{"header":"References","content":"\u003col start=\"1\" type=\"1\"\u003e\n \u003cli\u003eChang GJ, Rodriguez-Bigas MA, Skibber JM, Moyer VA. Lymph node evaluation and survival after curative resection of colon cancer: systematic review. \u003cem\u003eJ Natl Cancer Inst\u003c/em\u003e. 2007;99(6):433\u0026ndash;41.\u003c/li\u003e\n \u003cli\u003eEdge SB, Compton CC. The 7th edition of the AJCC cancer staging manual. \u003cem\u003eAnn Surg Oncol\u003c/em\u003e. 2010;17(6):1471\u0026ndash;4.\u003c/li\u003e\n \u003cli\u003eHa YH, et al. Influence of preoperative chemoradiotherapy on the number of lymph nodes retrieved in rectal cancer. \u003cem\u003eAnn Surg\u003c/em\u003e. 2010;252(2):336\u0026ndash;40.\u003c/li\u003e\n \u003cli\u003eWang H, et al. Patterns of lymph node metastasis differ in colon and rectal carcinomas. \u003cem\u003eWorld J Gastroenterol\u003c/em\u003e. 2010;16(43):5375\u0026ndash;9.\u003c/li\u003e\n \u003cli\u003eLe Voyer TE, et al. Colon cancer survival is associated with increasing number of lymph nodes analyzed. \u003cem\u003eJ Clin Oncol\u003c/em\u003e. 2003;21(3):2912\u0026ndash;9.\u003c/li\u003e\n \u003cli\u003eSwanson RS, et al. Prognosis of T3N0 colon cancer is dependent on the number of lymph nodes examined. \u003cem\u003eAnn Surg Oncol\u003c/em\u003e. 2003;10(1):65\u0026ndash;71.\u003c/li\u003e\n \u003cli\u003eBartels SA, et al. The effect of colonoscopic tattooing on lymph node retrieval. \u003cem\u003eGastrointest Endosc\u003c/em\u003e. 2012;76(4):793\u0026ndash;800.\u003c/li\u003e\n \u003cli\u003eCho YB, et al. Tumor localization for laparoscopic colorectal surgery. \u003cem\u003eWorld J Surg\u003c/em\u003e. 2007;31(7):1491\u0026ndash;5.\u003c/li\u003e\n \u003cli\u003eKang J, et al. Effect of preoperative colonoscopic tattooing on lymph node harvest in T1 colorectal cancer. \u003cem\u003eInt J Colorectal Dis\u003c/em\u003e. 2015;30(10):1349\u0026ndash;55.\u003c/li\u003e\n \u003cli\u003eBoni L, David G, Mangano A, et al. Clinical applications of indocyanine green (ICG) enhanced fluorescence in laparoscopic surgery. Surg Endosc. 2015;29(7):2046-2055.\u003c/li\u003e\n \u003cli\u003eSpatz H, et al. Sentinel lymph node mapping as a side-effect of colonoscopic tattooing. \u003cem\u003eSurg Endosc\u003c/em\u003e. 2010;24(3):589\u0026ndash;93.\u003c/li\u003e\n \u003cli\u003eDawson K, et al. Preoperative tattooing and improved lymph node retrieval rates. \u003cem\u003eArch Surg\u003c/em\u003e. 2010;145(9):826\u0026ndash;30.\u003c/li\u003e\n \u003cli\u003eFeinstein AR, et al. The Will Rogers phenomenon: stage migration and new diagnostic techniques. \u003cem\u003eN Engl J Med\u003c/em\u003e. 1985;312(25):1604\u0026ndash;8.\u003c/li\u003e\n\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":"","lastPublishedDoi":"10.21203/rs.3.rs-7164691/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7164691/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eBackground\u003c/strong\u003e: In patients with mid-to-lower rectal cancer undergoing neoadjuvant chemoradiotherapy (NACRT), lymph node (LN) retrieval is often suboptimal, affecting accurate staging and prognosis. Fluorescence-guided surgery (FGS) using Indocyanine Green (ICG) has emerged as a technique to enhance lymphatic mapping and identify aberrant lymph nodes (LNs) that may be missed while operating under conventional white light.\u003cbr\u003e\n\u003cstrong\u003eObjective:\u003c/strong\u003e To assess whether peri-tumoral tattooing with ICG and FGS alters the extent of lymphadenectomy and improves LN yield in rectal cancer patients post-NACRT.\u003cbr\u003e\n\u003cstrong\u003eMethods:\u003c/strong\u003e This investigator-initiated, quasi-experimental study utilized a prospectively maintained database from January 2023 to December 2024. Following 1:1 propensity score matching for eight variables (age, gender, BMI, tumor location, T-stage, N-stage, surgical procedure, and tattooing), 46 ICG-tattooed patients were compared to 46 controls. The primary outcome was the number of patients in whom FGS modified the extent of lymphadenectomy. Secondary outcomes included the number and positivity of aberrant LNs, and their size.\u003cbr\u003e\n\u003cstrong\u003eResults:\u003c/strong\u003e Median aberrant LNs identified was 2 per patient. The LN yield was significantly higher in the tattooed group (14 ± 3.7) than in the non-tattooed group (7 ± 3, P \u0026lt; 0.001). In 23 patients (50%), FGS altered the lymphadenectomy extent. Five aberrant nodes (10.87%) were malignant, located in stations 16B1, 16B2, and mesorectal sub-zones. The mean size of aberrant nodes was 4 ± 2 mm.\u003cbr\u003e\n\u003cstrong\u003eConclusion:\u003c/strong\u003e Fluorescence-guided lymphadenectomy significantly improves LN yield and aids in detecting small, otherwise occult, aberrant lymph nodes. ICG-guided techniques should be considered an adjunct to standard rectal cancer surgery following NACRT to ensure optimal oncologic outcomes.\u003c/p\u003e","manuscriptTitle":"FLARE Study – Fluorescence-guided Lymphadenectomy for augmented retrieval and Evaluation in Rectal Cancer surgery","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-08-04 13:42:22","doi":"10.21203/rs.3.rs-7164691/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":"34ed1bf2-6eae-421e-aa18-3be100024944","owner":[],"postedDate":"August 4th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-05-20T02:25:36+00:00","versionOfRecord":[],"versionCreatedAt":"2025-08-04 13:42:22","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7164691","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7164691","identity":"rs-7164691","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}