Benchmarking the Learning Curve of Minimally Invasive Rectal Cancer Surgery Using Textbook Outcome: A Retrospective Analysis of Laparoscopic, Robotic, and Transanal Rectal Cancer Resections

Benchmarking the Learning Curve of Minimally Invasive Rectal Cancer Surgery Using Textbook Outcome: A Retrospective Analysis of Laparoscopic, Robotic, and Transanal Rectal Cancer Resections | 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 Benchmarking the Learning Curve of Minimally Invasive Rectal Cancer Surgery Using Textbook Outcome: A Retrospective Analysis of Laparoscopic, Robotic, and Transanal Rectal Cancer Resections Rolf Riis, Margit Riis, Jūratė Šaltytė Benth, Knut Magne Augestad This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8507148/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 Aim The Textbook Outcome (TO) is a valuable tool for benchmarking but has not been used to evaluate the early learning curve of minimally invasive rectal cancer surgery. This retrospective study compared TO over a 10-year period across four surgical approaches to TME—open surgery (OPEN), laparoscopic (LAP), transanal (TaTME), and robotic (ROB)—focusing on the early learning-curve phase. Methods We examined 684 patients who underwent minimally invasive rectal cancer surgery from January 2014 to July 2024. TO was defined using an 8-point scoring system assessing operating time deviation, intraoperative complications (ClassIntra), postoperative complications (Clavien-Dindo III-V), length of stay >14 days or readmission within 30 days, mesorectal completeness, CRM ≤1mm, distal resection margin ≤1mm, lymph node harvest <12. Regression analysis was used to compare early learning curves in TO across surgical approaches. Results Patient demographics were similar across the OPEN (n=153), LAP (n=341), TaTME (n=54), and ROB (n=135) groups. ROB demonstrated consistent TO ratings from the beginning, the shortest average operating time (208 min, SD 60, overall p<0.001), and the lowest rate of perioperative complications (overall p=0.013). Overall, there were no significant differences among the groups regarding postoperative complications. The highest quality of mesorectal excision was observed in the robotic group (TaTME: 67.3%; OPEN: 84.6%; LAP: 87.9%; ROB: 88.9%; overall p<0.001). TaTME experienced early learning curve challenges in achieving TO, with first year cases showing a higher postoperative complication rate (overall p=0.030) and no TaTME cases meeting operating-time targets in the first year (overall p=0.029), although this improved within two years. Conclusion During the early learning phase, TaTME faced performance challenges, whereas laparoscopic and robotic TME implementation showed positive initial learning-curve results. The TO can serve as a standardized benchmark for assessing the quality of the early learning curve. Conducting regular intrahospital quality control of TO will verify whether the surgical work is of satisfactory quality or identify any aspects of the surgical procedure that need adjustment to achieve better results. Figures Figure 1 Figure 2 Figure 3 Figure 4 Strengths and Limitations of the Study A significant strength of this study is the use of the TO as a comprehensive, standardized quality metric to evaluate the early learning curve across multiple surgical approaches for rectal cancer excision over a prolonged 10-year period. The large, consecutive cohort and inclusion of open, laparoscopic, transanal, and robotic techniques allowed for direct comparison of implementation phases within a single institutional setting, minimizing variability related to case selection and perioperative care. This study has several limitations. Its retrospective, single-center design may limit generalizability and introduce potential selection and temporal biases, particularly as surgical techniques and perioperative management have evolved over time. In addition, surgeon-specific experience and case volume could not be fully adjusted for and may have influenced learning-curve performance, especially for TaTME. Finally, although textbook outcome captures multiple dimensions of surgical quality, it does not account for patient-reported outcomes or long-term oncological endpoints. Introduction Over the past decades, surgical techniques for rectal cancer have shifted from open surgery to various minimally invasive methods. It is crucial that these advancements improve patient outcomes and that the learning curve is associated with a minimal number of adverse events. All hospitals should implement a monitoring system to ensure that both established and new surgical techniques deliver the best possible results for patients. Benchmarking minimally invasive surgical techniques against textbook outcomes (TO) could be such a method. A TO refers to a situation in which the patient's recovery unfolds precisely as anticipated. In this paper, a "textbook outcome" refers to a patient's recovery following standard surgical treatment, in which all events unfold as expected. ( 1 – 5 ) Surgeons may face challenges, such as longer operating times and higher complication rates, during their early experience with new techniques. This phenomenon is well-documented across various surgical fields, indicating that learning curves vary significantly between procedures. ( 6 – 8 ). In rectal cancer surgery, it is shown that the early learning curve is associated with an increased rate of local recurrences and worse short-term outcomes. ( 9 – 12 ). Therefore, it is essential to monitor the implementation of new minimally invasive techniques and to actively use benchmarking tools. The use of TO as a benchmarking tool during the implementation of new surgical techniques in minimally invasive rectal cancer surgery has not yet been described in the literature, and we hypothesized that TO is a valuable tool for this purpose. Based on this, the study aimed to use TO to benchmark surgical quality during the learning curve of laparoscopic rectal resection (LAP), trans-anal total mesorectal excision (TaTME), and robotic-assisted rectal resection (ROB), and to compare these results with open rectal resection (OPEN), which was regarded as the gold standard. Material and Methods Study design This is a single-center retrospective cohort study of rectal cancer patients who underwent curative surgery at Akershus University Hospital from 1 January 2014 to 31 July 2024. The hospital data security board approved this project as a quality improvement study (PVO case number 2018-061), and therefore, informed consent is not required under Norwegian law. The data used in the study originated from a prospectively collected quality registry. Implementation of minimal invasive rectal cancer surgery During the study period, three minimally invasive techniques for rectal cancer surgery were introduced in chronological order: laparoscopic TME, transanal TME, and robotic TME. The use of open rectal cancer surgery remained consistent but was gradually replaced by laparoscopic and robotic procedures. TaTME was employed for four years, but, according to national regulations, it was discontinued in 2018. ( 13 ) Before the implementation of MIS, surgeons underwent proctoring and obtained certification for the surgical procedure. Inclusion criteria: Patients diagnosed with rectal cancer are defined as those with adenocarcinoma located less than 15 cm from the anal verge. All patients underwent one of four surgical procedures: OPEN, LAP, ROB, or TaTME. Exclusion criteria: Patients with synchronous colon cancer and those with locally advanced cancer requiring beyond-TME /PME surgery. Primary and secondary outcomes: The primary outcome was the TO rate in OPEN, LAP, TaTME, and ROB during the first years of introduction. Secondary outcome measures included the association between operating time, surgical quality, oncological specimen quality, and post-operative complications within 30 days. Variables of interest: Include sex, BMI, ASA score, tumor distance from the anal verge (AV), tumor size, MRI tumor stage (I-IV), neoadjuvant chemoradiotherapy, distance from the anal verge to the anastomosis (cm), deviating stoma, and length of hospital stay (days). Surgical procedures: high anterior resection with partial mesorectal excision (PME); low anterior resection with total mesorectal excision (TME); PME/TME with end colostomy (Hartmann); abdominoperineal resection (APR); and transanal total mesorectal excision (TaTME) with or without primary anastomosis; Skin-to-skin operating time was recorded. Intraoperative surgical complications were classified according to the ClassIntra classification system, and postoperative complications up to 30 days were classified according to the Clavien-Dindo system. ( 14 , 15 ) Length of stay was defined as the days from surgery to hospital discharge, and readmissions within 30 days were also recorded. Definition of textbook outcome A patient pathway with optimal surgical technique, free from per- and postoperative complications, an ideal oncological specimen, an optimal length of stay, and no readmissions was classified as a TO. A TO scoring system was implemented and prospectively measured to assess the overall quality of the surgery. The scoring system was based on the Norwegian national guidelines for colorectal cancer and classification systems for intraoperative and postoperative surgical complications. ( 14 – 17 ) Thus, a TO for the early learning curve of minimal invasive rectal cancer was defined as achieving 8 points after evaluating the patient pathway up to 30 days following hospital discharge, based on the following quality measurements: no deviation from the median skin-to-skin operating time > 30%; no intraoperative complications according to the ClassIntra classification grade > II; no postoperative complications up to 30 days according to the Clavien-Dindo classification stage III-V; no deviation from LOS > 14 days and/or readmission within 30 days; a complete or nearly complete mesorectum, according to Quirke; a distance to CRM > 1mm; distal resection margin > 1mm; and the number of lymph nodes ≥ 12. There was only one death within 30 days; a separate variable for this was dropped. Statistical Methods Patient characteristics, complications and oncological outcomes were presented as means and standard deviations (SDs) for continuous variables and as frequencies and percentages for categorical variables. Median and first and third quartiles were included for skewed continuous variables. ANOVA and the χ2 test were used to assess overall between-group differences. Post hoc analyses, considered purely exploratory, were performed to assess pairwise differences between OPEN and the three other surgery groups. Linear regression models for continuous outcomes and logistic regression models for dichotomous outcomes were estimated to assess differences between groups in the change in either the mean or the odds over time. The models included time as a second-order polynomial, group and the interaction between time and group. A significant interaction term would imply significant between-group differences in change in time. Post hoc analyses were performed to assess within-group changes and between-group differences at each time point. The results of the regression models were tabulated as regression coefficients and standard errors. Because surgeries were performed across different time periods, the first year of surgery introduction was used as the index time point. Only one LAP surgery was performed in 2014, and four or fewer OPEN surgeries were performed after 2017; these were excluded from the analyses. All statistical analyses were performed in STATA v18. Results with p-values below 0.05 were considered statistically significant. No adjustment for multiple testing was implemented. Results Demographics The study involved 684 patients, with a mean age of 66.5 years (SD 11.6), a mean BMI of 26.2 (SD 4.6), and 38% were women. The OPEN group included n=153 patients; the LAP group, n=341; the ROB group, n=135; and the TaTME group, n=55. Patient characteristics are presented in Table 1. The mean distance from the tumor to the anal verge (AV) was 8.4 cm (SD 3.5) and was shortest in the TaTME group (overall p<0.001 and overall differences were significant between Open and the three other groups (p=0.036 for LAP, p=0.012 for taTME and p=0.039 for ROB). The mean tumor size was 4.3 cm (SD 2.7), which did not differ between the groups. The MRI staging of the tumor (measured in 681 out of 684 cases) showed 26.7% stage I, 42% stage II, 24.4% stage III, and 6.9% stage IV. In the TaTME group, only 18.2% of tumors were stage I and 32.7% were stage III. In the OPEN group, only 31.6% of tumors were stage II and 13.8% stage IV. Overall, between-group differences were significant (p=0.001), but overall differences were significant only for Open vs. LAP (p<0.001) and Open vs. ROB (p=0.020). The need for neoadjuvant systemic treatment was highest in the OPEN group (32.7%) and lowest in the LAP group (24%), with no significant between-group differences. Implementation of Minimal Invasive Surgery The LAP method was introduced in 2015, and 15 patients were operated on with this procedure the first year. In 2019 and 2020, all but one occurrence included LAP. TaTME was launched in 2015 in collaboration with LAP but recorded only 5 cases that year. It reached 26 cases in 2018 but was discontinued due to national concerns about multifocal local recurrences. (13) The ROB-assisted technique was first performed in 2021on 11 cases. In 2023, ROB was used in 75% cases, rising to 92% by July 2024. Due to enhanced access to the Da Vinci robot, no rectal tumors were treated with LAP in 2024 (Supplemental Table 1). Intraoperative complications A total of 298 of 398 patients (74.9%) with primary anastomosis received a temporary diverting stoma, which was most common in the TaTME group where all had diverting stoma. The overall conversion rate was 9.4%. It was highest in the LAP group at 13.2% and lowest in the ROB group at only 1.5%. All patients with operating time > 268 minutes achieved TO = 1. The overall median operating time was 206 minutes (Q1-Q3 164-259 minutes), 196 minutes in the ROB group, 197 minutes in the OPEN group, 203 minutes in the LAP group and 270 minutes in the TaTME group (overall p<0.001). Still, only the groups OPEN vs. taTME differed significantly (p < 0.001). Figure 1A shows the percentage of cases in the study period that operated within the established time limit. According to the logistic regression model (Table 5), there were no significant differences between OPEN and other groups in change in odds of median operating time within 268 minutes, but TaTME group had overall significantly lower odds than the OPEN group (p=0.029). Post hoc analysis suggests no significant trend in the four groups. However, the TaTME group had significantly lower odds of operating time, less than 268 minutes. than the OPEN group at years 1, 2, and 4 (all p=0.009). The total intraoperative complications over the year following the implementation of a new surgical procedure are shown in Figure 1B and Table 2. Eighty percent of TaTME and LAP patients experienced no intraoperative complications during the first year, but this figure dropped to below 75% by the fourth year. The ROB procedure reported no perioperative complications in its first year and remained steady at around 90% in subsequent years. The OPEN procedure had only 10% complications from 2014 to 2017, which increased to about 20% in 2016. According to the logistic regression model (Table 5), there is no difference between OPEN and other groups in change in odds of perioperative complications (no significant interactions between time and operating type) and no overall differences in odds of intraoperative complications. Postoperative complications According to Table 3, overall, 20.7% of patients experienced postoperative complications, and there were no significant differences between the groups. 8.3% of patients with an anastomosis experienced an anastomotic leak: OPEN 6.2%, LAP 9.3%, TaTME 11.6%, and ROB 6.2%. 87 patients (12.7%) remained in hospital for more than 14 days, with 18% in the OPEN and TaTME groups and 10% in the LAP and ROB groups. Figures 3C show the percentage of TO in achieving no postoperative complications, no LOS over 14 days, and/or readmissions within 30 days. All five TaTME-operated patients in the first year, experienced postoperative complications, but their rates did not differ from those of other groups in subsequent years. According to the logistic regression model (Table 5), there is no difference between the OPEN group and the others in change in odds and no difference in the overall odds for LOS over 14 days. Post hoc analyses revealed no significant trend in the OPEN, LAP, and ROB groups; however, the change in the TaTME group between year 1 and 2 was significant (p=0.049). Moreover, the TaTME group had significantly lower odds of LOS over 14 days than the OPEN group at year 1 (p=0.030). Oncological outcomes The distance from tumor tissue to the CRM is ≤1 mm in 11.4% of cases, the lowest in the ROB group at 8.9% and highest in the TaTME group with 21.8% (overall p=0.014 with no significant overall differences). According to Quirke, the mesorectum is either complete or nearly complete in 85.7% of cases, demonstrating the best performance in the ROB group (88.9%) and underperforming in the TaTME group (67.3%; overall p<0.001 and the only significant overall difference between OPEN and taTME, p=0.008). The distance from the distal resection (DR) to tumor tissue was ≤1 mm in only 2 cases: 1 in the TaTME group and 1 in the ROB group. In 92.5% of cases, the specimen contained at least 12 lymph nodes (Table 4). Figure 1D illustrates the percentage of TOs related to oncological quality. According to the logistic regression model (Table 5), there is no difference between OPEN and other groups in the change in the odds and in the overall odds of no oncological adverse outcome. Textbook outcome A TO was achieved in 38% of all the patients in this study. When combined with all cases achieving near complete TO (≥7), the total rises to 66.2%. In 5.6% of cases, the score was below five on the TO scale. Even in the well-established OPEN group, the TO rate did not exceed 32% over the 4 years. However, the ROB group (37.8%) and the LAP group (36.3%) had better average TO rates. The TaTME group had only an average TO of 22%, and during the first year with TaTME, none of the patients achieved TO. Nonetheless, over the following three years, the method stabilized a TO between 55% and 59% (Figures 2 and 3). The distribution of TO points during the first four years differed across surgical approaches (Figure 4). In Years 1 and 2, robotic and laparoscopic TME had a higher proportion of patients achieving ≥7 TO points than open surgery and TaTME. Robotic TME showed the most consistent performance across all four years, with a steady proportion of patients reaching the highest TO category (≥7 points). TaTME exhibited a distinct early learning-curve pattern, characterized by a higher proportion of patients with <5 TO points in Year 1 and an absence of patients achieving ≥7 TO points. Performance improved progressively over subsequent years, with a larger proportion of patients reaching higher TO categories by Years 3 and 4. Open surgery demonstrated intermediate performance, with gradual improvement over time but greater variability than laparoscopic and robotic approaches. According to the linear regression model (Table 5), the change in the TaTME group differs significantly from that in the OPEN group (p=0.002 and p=0.006 for the interaction between time and operation type). Discussion In this study, we have demonstrated that, compared to the gold standard of open surgery, laparoscopic and robotic surgery achieved acceptable quality measures and TO during the early learning curve. Conversely, this study indicates that TaTME has experienced performance issues related to skin-to-skin operating time, increased length of stay, and readmissions, and, overall, shows poor performance with respect to TO. Research in context Our study aligns with other studies related to the TO. Warps et al. conducted a study to evaluate TO after rectal cancer surgery as a short-term quality-of-care measure. Patients who underwent rectal cancer surgery between 2012 and 2019 were included. TO was defined as being alive at 30 days or during the primary admission, without reinfection, complications, or readmission, with a hospital stay of no more than 14 days and having tumor-free margins. 56.3% achieved TO and concluded that postoperative complications mainly influence rectal cancer outcomes. In their view, TO does not align with the plan-do-check-act cycle of clinical auditing. They also believed that TO adds little value to current outcome indicators for rectal cancer surgery. ( 17 ) Mac Curtain et al. conducted a systematic review of 15 studies involving 301,502 patients and found that TO was achieved in an average of 55% of reported cases. The paper concluded that there is no standardized definition of TO in use, and that a Delphi consensus is warranted to enable meaningful comparisons using TO in the future. ( 1 ) Arrighini et al concluded in their paper that TO is an effective indicator for assessing the quality of colorectal cancer surgery. By standardizing TO parameters, they believe the consistency and quality of care across institutions can be enhanced. The authors suggest a unified definition of TO for colorectal surgery: radical resection, LN yield ≥ 12, no Clavien-Dindo ≥ III, length of stay (75th percentile), no 30-day readmissions, and no 30-day mortality. ( 18 ) These studies use TO to compare colorectal cancer care across different institutions, rather than to analyze intra-hospital early learning curves for minimally invasive rectal cancer surgery. The higher number of TO variables in our study (n = 8) might explain why the TO rate here is lower than reported in other studies. Oncological outcomes In previous studies assessing TO, the quality of the mesorectum is not included in the TO assessment. Without this variable, the total percentage of a “perfect oncological outcome” rises from 72–82%, and the total number of TO rises to 38.7%. The overall numbers with near complete TO (≥ 7 points) are 64% in OPEN group, 65.9% in the ROB group, 67% LAP group 1–4, and 73.8% LAP group 5–9. On the other hand, the TaTME group are significantly lower with only 38.9% This supports the importance of including oncological outcomes to obtain comparable values for TO. Operating time Operating time during the implementation of a new surgical procedure may be longer than that for established techniques. This is why operating time is treated as a variable in this study and in all surgical learning-curve studies. We observed no significant differences between the OPEN and other groups, except for TaTME, in overall odds for operating time within 268 minutes (median time + 30%). TaTME is a challenging surgery performed by two teams and remains difficult despite mentorship and global training. The TaTME approach was only used for patients with rectal cancer less than 10 cm from the anal margin, resulting in longer dissection times than for other groups also including high rectal tumors. TaTME use was discontinued after 55 cases, but the steep learning curve suggests that, by 100 cases, operating time could be comparable to that of other procedures. The initial 30 robotic-assisted rectal surgery operations were limited to women with low, mid, and high rectal cancer and men with high rectal cancer, excluding neoadjuvant-treated patients. Due to successful procedures, these exclusion criteria were lifted after 15 cases. No exclusion criteria were used when we started laparoscopic rectal cancer treatment. Still, the first 15 LAP patients (year 1) had a higher TO = 1 score for operating time than the other groups. This is challenging to explain, yet 40 of 60 patients that year underwent open surgery, suggesting that more complex cases were selected. However, except in the TaTME group, novel rectal surgical approaches have not considerably extended operating time throughout the learning curve. Intraoperative complications The TO score shows that the TaTME group did not differ significantly from the other groups across the four years regarding intraoperative complications. According to ClassIntra classification, the TaTME group experienced five (45%) grade 3 complications, including two severe urethral injuries, a well-known complication associated with the trans anal approach. The robotic group experienced no intraoperative complications out of the 11 cases in the first year and scored 1 point due to TO in about 90% of cases across the four first years. The overall perioperative complication rate for the ROB group is 9.6% (the lowest of all groups), but 10 out of 13 perioperative complications (76.9%) are classified as Grade 3. Post hoc analyses show that in the second year, the LAP group has significantly lower odds of perioperative complications than the OPEN group. Postoperative complications At year 1, all five patients with TaTME experienced postoperative complications, with odds significantly different from the OPEN group (p = 0.030). By year 2, approximately 65% of the TaTME group scored on the TO scale. The ROB group had the lowest percentage of LOS ≥ 14 days (9.6%); however, it also had the highest readmission rate (28.1%), compared with OPEN (19%) and LAP (17.3%). One possible reason for this could be early discharges from hospital within the ROB group and a higher incidence of presacral abscesses that were not diagnosed during the initial hospitalization. Limitations Limitations exist. This is a retrospective study, and patient selection for each surgical procedure depended on the availability of skilled surgeons and robots, the patients’ BMI (obesity, narrow pelvis), previous abdominal surgery, and comorbidities. Patients without complications, with a LOS of less than 14 days, and who are not readmitted within 30 days achieve TO. Conversely, a patient with a postoperative complication, who remains in hospital for more than 14 days or is readmitted within 30 days, will unlikely achieve TO ≥ 7 due to one complication. This may introduce bias into the study and supports the conclusion of the Warp review article.( 17 ) The number of mobilizations of the splenic flexure varies across the four groups: 25 (16.3%) in the OPEN group, 202 (59.2%) in the LAP group, 78 (57.8%) in the ROB group, and 47 (85.5%) in the TaTME group. It generally takes about 30 to 60 minutes to mobilize the splenic flexure. This paper does not account for this because the operating description does not specify precisely how long it took to mobilize the left flexure. This study does not distinguish between high and low anterior resection, which is a limitation because the TaTME group includes only low rectal cancers (below 10cm from AV). The reasons for including high rectal cancers are the relatively small number of these cancers diagnosed each year and the fact that most surgical steps are similar in high and low rectal cancer procedures. In the TaTME group, there are significantly more cases with anastomosis than in the other groups, leading to a higher risk of anastomosis-related complications. Since TaTME involves both an abdominal and a transanal approach, with the latter being relatively unfamiliar to surgeons, the skin-to-skin operating time is longer. This, combined with only 5 cases in the first year, an overall lower tumor stage, a notably higher number of anastomoses, and the fact that the procedure was cancelled after 55 cases, makes it difficult to determine whether it would have been possible to achieve the same TO as the LAP and ROB groups after approximately 100–150 cases.( 13 ) Strengths The study relies on a meticulously collected quality registry spanning 10 years, which enables the assessment of the implementation and early learning curve of three minimally invasive rectal cancer surgery methods. To our knowledge, this has not been done by others, thereby enhancing the study's uniqueness. Four surgeons at the hospital performed most of the minimally invasive surgical procedures. This suggests that, when transitioning from laparoscopic to robot-assisted surgery, these five surgeons were well trained in minimally invasive rectal surgery, which likely steepened the learning curve and provided acceptable TO. Conclusions For surgical departments, it is crucial not only to analyze TO during the early learning curve of minimally invasive rectal cancer surgery but also to conduct a detailed examination of quality measures, including operating time, perioperative complications, postoperative events, and oncological outcomes. Regular intrahospital quality control of these parameters during MIS implementation will ensure surgical work is of satisfactory quality or identify aspects of the surgical procedure that need adjustment to achieve better results. During the early learning curve, TaTME encountered performance challenges, whereas laparoscopic and robotic TME showed positive initial learning curve results. The TO can serve as a standardized in-hospital benchmark for assessing the quality of the early learning curve. Declarations Acknowledgements: We thank all operating surgeons and RN at the CRC team at the Department of Gastrointestinal Surgery, Akershus University Hospital. Author contribution Rolf Riis: Conceptualization, Methodology, Validation, Investigation, Data Curation, Writing – Original Draft, Writing – Review Knut Magne Augestad: Conceptualization, Methodology, Validation, Investigation, Writing – Original Draft, Writing – Review, Supervision, Funding. Jūratė Šaltytė Benth: Methodology, Software, Validation, Formal Analysis, Investigation, Visualisation, Supervison. Margit Riis: Data Curation, Writing – Original Draft; Writing -Review, Analyses, Visualisation. Funding: This research was funded by a grant from the Division of Surgery, Akershus University Hospital, Lørenskog, Norway. Data sharing: Under Norwegian law, data sharing is not permitted. References Mac Curtain BM, Qian W, O'Mahony A, Deshwal A, Mac Curtain RD, Temperley HC, et al. "Textbook outcome(s)" in colorectal surgery: a systematic review and meta-analysis. Ir J Med Sci. 2024;193(5):2187–94. Aly M, Chang Y-H, Stucky C-C, Fong ZV, Etzioni D, Wasif N. 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ANZ J Surg. 2022;92(3):355–64. Gachabayov M, You K, Kim SH, Yamaguchi T, Jimenez-Rodriguez R, Kuo LJ, et al. Meta-Analysis of the Impact of the Learning Curve in Robotic Rectal Cancer Surgery on Histopathologic Outcomes. Surg Technol Int. 2019;34:139–55. Riis RN, Riis MH, Benth JS, Augestad KM. Beyond the transanal total mesorectal excision moratorium: local and distant recurrence among patients operated for low rectal tumors-5-year follow-up from a Norwegian University Hospital. Br J Surg. 2023. Dell-Kuster S, Gomes NV, Gawria L, Aghlmandi S, Aduse-Poku M, Bissett I, et al. Prospective validation of classification of intraoperative adverse events (ClassIntra): international, multicentre cohort study. BMJ. 2020;370:m2917. Clavien PA, Barkun J, de Oliveira ML, Vauthey JN, Dindo D, Schulick RD, et al. The Clavien-Dindo classification of surgical complications: five-year experience. Ann Surg. 2009;250(2):187–96. Dindo D, Demartines N, Clavien PA. Classification of surgical complications: a new proposal with evaluation in a cohort of 6336 patients and results of a survey. Ann Surg. 2004;240(2):205–13. Warps AK, Detering R, Tollenaar R, Tanis PJ, Dekker JWT, Dutch ColoRectal Audit g. Textbook outcome after rectal cancer surgery as a composite measure for quality of care: A population-based study. Eur J Surg Oncol. 2021. Arrighini GS, Martinino A, Zecchin Ferrara V, Lorenzon L, Giovinazzo F. Textbook oncologic outcomes in colorectal cancer surgery: a systematic review. Frontiers in Oncology. 2025;15. Tables Tables 1 to 5 are available in the Supplementary Files section. Additional Declarations No competing interests reported. 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12:00:08","extension":"html","order_by":24,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":131778,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-8507148/v1/604966849cacd39b4c3a16b6.html"},{"id":100401681,"identity":"9edd4028-9ea0-4d94-b84b-006e83534d84","added_by":"auto","created_at":"2026-01-16 11:59:09","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":258979,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eA-D. Learning curves of individual textbook outcome (TO) components by surgical approach over time.\u003cbr\u003e\n \u003c/strong\u003eLine graphs show the annual proportion for patients achieving TO criteria for (A) skin-to-skin operating time ≤268 minutes, (B) absence of perioperative complications, (C) length of stay \u0026lt;14 days and/or no readmission within 30 days, and (D) oncological outcomes (complete mesorectal excision, negative circumferential and distal margins, and adequate lymph node harvest). Results are shown for open surgery, laparoscopic, transanal total mesorectal excision (TaTME), and robotic approaches across consecutive years of implementation. Robotic and laparoscopic TME demonstrate stable favorable performance from early implementation, whereas TaTME shows pronounced early learning-curve effects with progressive improvement over time.\u003c/p\u003e","description":"","filename":"Figure1ABCDtruncatedat8yrs.png","url":"https://assets-eu.researchsquare.com/files/rs-8507148/v1/996a835fd7b7dd2dad8ce32a.png"},{"id":100401871,"identity":"28865732-c9be-4b77-b3d0-c4cfbfbfa602","added_by":"auto","created_at":"2026-01-16 11:59:23","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":954628,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eOverall textbook outcome achievement during the early learning curve of minimally invasive rectal cancer surgery.\u003c/strong\u003e\u003cbr\u003e\nThe figure shows the annual proportion of patients achieving an overall textbook outcome (TO) following open, laparoscopic, transanal total mesorectal excision (TaTME), and robotic rectal cancer surgery. Laparoscopic and robotic approaches show a progressive increase in TO achievement over time, whereas TaTME shows pronounced early learning-curve effects with low initial TO rates followed by transient improvement. Open surgery shows greater year-to-year variability, reflecting changes in case mix and institutional practice during the study period.\u003c/p\u003e","description":"","filename":"Figure2truncatedat8yrs.png","url":"https://assets-eu.researchsquare.com/files/rs-8507148/v1/d242a5d5dfb8f23e131a5003.png"},{"id":100401875,"identity":"8446cc82-d703-4d30-824a-11bf434d9f3d","added_by":"auto","created_at":"2026-01-16 11:59:23","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":1456441,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eProportion of patients achieving ≥7 textbook outcome (TO) points during the early learning curve of minimally invasive rectal cancer surgery.\u003c/strong\u003e\u003cbr\u003e\nThe figure illustrates annual rates of overall TO achievement (≥7 points) for open surgery, laparoscopic, transanal total mesorectal excision (TaTME), and robotic approaches. Laparoscopic and robotic TME demonstrate consistently high TO rates from early implementation with progressive stabilization over time. In contrast, TaTME shows marked early learning-curve effects, with low initial TO rates and gradual improvement, whereas open surgery exhibits greater inter-year variability.\u003c/p\u003e","description":"","filename":"Figure3truncatedat8yrs.png","url":"https://assets-eu.researchsquare.com/files/rs-8507148/v1/80423e842ad6fde1992cc6e0.png"},{"id":100402142,"identity":"73e264ea-a369-4f4d-b5cb-a3ace554eef7","added_by":"auto","created_at":"2026-01-16 11:59:44","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":165166,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ePercentage distribution of textbook outcome (TO) points by surgical approach during the first four years of implementation.\u003c/strong\u003e\u003cbr\u003e\nHeatmap illustrating the proportion of patients achieving different TO point categories (\u0026lt;5, 7, 8, and ≥7 points) for open, laparoscopic (Lap), robotic (ROB), and transanal total mesorectal excision (TaTME) in Years 1–4. Darker shading indicates a higher percentage of patients within a given category. TaTME demonstrates an early learning-curve effect with lower TO scores in Year 1, followed by progressive improvement. In contrast, laparoscopic and robotic approaches show more stable and favorable TO distributions from early implementation.\u003c/p\u003e","description":"","filename":"Figure4TOHeatmapYears14greyscaledynamictext.png","url":"https://assets-eu.researchsquare.com/files/rs-8507148/v1/78f073799a90c4ff039904fa.png"},{"id":104565083,"identity":"bab37404-6633-43f5-8fbb-ef90c9f7ae4d","added_by":"auto","created_at":"2026-03-13 11:11:59","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3729869,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8507148/v1/7b06668f-1249-493b-92d0-b4f6782d104c.pdf"},{"id":100402530,"identity":"ab3feaa0-93d0-4cb8-8898-805eed153a10","added_by":"auto","created_at":"2026-01-16 12:00:20","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":39256,"visible":true,"origin":"","legend":"","description":"","filename":"tables2.docx","url":"https://assets-eu.researchsquare.com/files/rs-8507148/v1/9cdbdc21a0ed6b28cda2676f.docx"},{"id":100402591,"identity":"9d8d4368-4866-4241-9edb-0b1bc30f9343","added_by":"auto","created_at":"2026-01-16 12:00:23","extension":"docx","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":16426,"visible":true,"origin":"","legend":"","description":"","filename":"suppltable.docx","url":"https://assets-eu.researchsquare.com/files/rs-8507148/v1/fbe4cb5d7400155901237ef8.docx"},{"id":100402108,"identity":"4bbf9d4a-dbd1-4dd5-a50c-a7c2d0a26434","added_by":"auto","created_at":"2026-01-16 11:59:44","extension":"tif","order_by":3,"title":"","display":"","copyAsset":false,"role":"supplement","size":251735,"visible":true,"origin":"","legend":"","description":"","filename":"graphicabstract.tif","url":"https://assets-eu.researchsquare.com/files/rs-8507148/v1/184fdd0fde56a6c28e9d42a0.tif"}],"financialInterests":"No competing interests reported.","formattedTitle":"\u003cp\u003eBenchmarking the Learning Curve of Minimally Invasive Rectal Cancer Surgery Using Textbook Outcome: A Retrospective Analysis of Laparoscopic, Robotic, and Transanal Rectal Cancer Resections\u003c/p\u003e","fulltext":[{"header":"Strengths and Limitations of the Study","content":"\u003cp\u003eA significant strength of this study is the use of the TO as a comprehensive, standardized quality metric to evaluate the early learning curve across multiple surgical approaches for rectal cancer excision over a prolonged 10-year period. The large, consecutive cohort and inclusion of open, laparoscopic, transanal, and robotic techniques allowed for direct comparison of implementation phases within a single institutional setting, minimizing variability related to case selection and perioperative care.\u003c/p\u003e\n\u003cp\u003eThis study has several limitations. Its retrospective, single-center design may limit generalizability and introduce potential selection and temporal biases, particularly as surgical techniques and perioperative management have evolved over time. In addition, surgeon-specific experience and case volume could not be fully adjusted for and may have influenced learning-curve performance, especially for TaTME. Finally, although textbook outcome captures multiple dimensions of surgical quality, it does not account for patient-reported outcomes or long-term oncological endpoints.\u003c/p\u003e"},{"header":"Introduction","content":"\u003cp\u003eOver the past decades, surgical techniques for rectal cancer have shifted from open surgery to various minimally invasive methods. It is crucial that these advancements improve patient outcomes and that the learning curve is associated with a minimal number of adverse events. All hospitals should implement a monitoring system to ensure that both established and new surgical techniques deliver the best possible results for patients. Benchmarking minimally invasive surgical techniques against textbook outcomes (TO) could be such a method. A TO refers to a situation in which the patient's recovery unfolds precisely as anticipated. In this paper, a \"textbook outcome\" refers to a patient's recovery following standard surgical treatment, in which all events unfold as expected. (\u003cspan additionalcitationids=\"CR2 CR3 CR4\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e)\u003c/p\u003e \u003cp\u003eSurgeons may face challenges, such as longer operating times and higher complication rates, during their early experience with new techniques. This phenomenon is well-documented across various surgical fields, indicating that learning curves vary significantly between procedures. (\u003cspan additionalcitationids=\"CR7\" citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e). In rectal cancer surgery, it is shown that the early learning curve is associated with an increased rate of local recurrences and worse short-term outcomes. (\u003cspan additionalcitationids=\"CR10 CR11\" citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e). Therefore, it is essential to monitor the implementation of new minimally invasive techniques and to actively use benchmarking tools. The use of TO as a benchmarking tool during the implementation of new surgical techniques in minimally invasive rectal cancer surgery has not yet been described in the literature, and we hypothesized that TO is a valuable tool for this purpose.\u003c/p\u003e \u003cp\u003eBased on this, the study aimed to use TO to benchmark surgical quality during the learning curve of laparoscopic rectal resection (LAP), trans-anal total mesorectal excision (TaTME), and robotic-assisted rectal resection (ROB), and to compare these results with open rectal resection (OPEN), which was regarded as the gold standard.\u003c/p\u003e"},{"header":"Material and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eStudy design\u003c/h2\u003e \u003cp\u003eThis is a single-center retrospective cohort study of rectal cancer patients who underwent curative surgery at Akershus University Hospital from 1 January 2014 to 31 July 2024. The hospital data security board approved this project as a quality improvement study (PVO case number 2018-061), and therefore, informed consent is not required under Norwegian law. The data used in the study originated from a prospectively collected quality registry.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eImplementation of minimal invasive rectal cancer surgery\u003c/h3\u003e\n\u003cp\u003eDuring the study period, three minimally invasive techniques for rectal cancer surgery were introduced in chronological order: laparoscopic TME, transanal TME, and robotic TME. The use of open rectal cancer surgery remained consistent but was gradually replaced by laparoscopic and robotic procedures. TaTME was employed for four years, but, according to national regulations, it was discontinued in 2018. (\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e) Before the implementation of MIS, surgeons underwent proctoring and obtained certification for the surgical procedure.\u003c/p\u003e\n\u003ch3\u003eInclusion criteria:\u003c/h3\u003e\n\u003cp\u003ePatients diagnosed with rectal cancer are defined as those with adenocarcinoma located less than 15 cm from the anal verge. All patients underwent one of four surgical procedures: OPEN, LAP, ROB, or TaTME.\u003c/p\u003e\n\u003ch3\u003eExclusion criteria:\u003c/h3\u003e\n\u003cp\u003ePatients with synchronous colon cancer and those with locally advanced cancer requiring beyond-TME /PME surgery.\u003c/p\u003e\n\u003ch3\u003ePrimary and secondary outcomes:\u003c/h3\u003e\n\u003cp\u003eThe primary outcome was the TO rate in OPEN, LAP, TaTME, and ROB during the first years of introduction. Secondary outcome measures included the association between operating time, surgical quality, oncological specimen quality, and post-operative complications within 30 days.\u003c/p\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eVariables of interest:\u003c/h2\u003e \u003cp\u003eInclude sex, BMI, ASA score, tumor distance from the anal verge (AV), tumor size, MRI tumor stage (I-IV), neoadjuvant chemoradiotherapy, distance from the anal verge to the anastomosis (cm), deviating stoma, and length of hospital stay (days). Surgical procedures: high anterior resection with partial mesorectal excision (PME); low anterior resection with total mesorectal excision (TME); PME/TME with end colostomy (Hartmann); abdominoperineal resection (APR); and transanal total mesorectal excision (TaTME) with or without primary anastomosis; Skin-to-skin operating time was recorded. Intraoperative surgical complications were classified according to the ClassIntra classification system, and postoperative complications up to 30 days were classified according to the Clavien-Dindo system. (\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e) Length of stay was defined as the days from surgery to hospital discharge, and readmissions within 30 days were also recorded.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eDefinition of textbook outcome\u003c/h3\u003e\n\u003cp\u003eA patient pathway with optimal surgical technique, free from per- and postoperative complications, an ideal oncological specimen, an optimal length of stay, and no readmissions was classified as a TO. A TO scoring system was implemented and prospectively measured to assess the overall quality of the surgery. The scoring system was based on the Norwegian national guidelines for colorectal cancer and classification systems for intraoperative and postoperative surgical complications. (\u003cspan additionalcitationids=\"CR15 CR16\" citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e)\u003c/p\u003e \u003cp\u003eThus, a TO for the early learning curve of minimal invasive rectal cancer was defined as achieving 8 points after evaluating the patient pathway up to 30 days following hospital discharge, based on the following quality measurements: no deviation from the median skin-to-skin operating time\u0026thinsp;\u0026gt;\u0026thinsp;30%; no intraoperative complications according to the ClassIntra classification grade\u0026thinsp;\u0026gt;\u0026thinsp;II; no postoperative complications up to 30 days according to the Clavien-Dindo classification stage III-V; no deviation from LOS\u0026thinsp;\u0026gt;\u0026thinsp;14 days and/or readmission within 30 days; a complete or nearly complete mesorectum, according to Quirke; a distance to CRM\u0026thinsp;\u0026gt;\u0026thinsp;1mm; distal resection margin\u0026thinsp;\u0026gt;\u0026thinsp;1mm; and the number of lymph nodes\u0026thinsp;\u0026ge;\u0026thinsp;12. There was only one death within 30 days; a separate variable for this was dropped.\u003c/p\u003e\n\u003ch3\u003eStatistical Methods\u003c/h3\u003e\n\u003cp\u003ePatient characteristics, complications and oncological outcomes were presented as means and standard deviations (SDs) for continuous variables and as frequencies and percentages for categorical variables. Median and first and third quartiles were included for skewed continuous variables. ANOVA and the χ2 test were used to assess overall between-group differences. Post hoc analyses, considered purely exploratory, were performed to assess pairwise differences between OPEN and the three other surgery groups.\u003c/p\u003e \u003cp\u003eLinear regression models for continuous outcomes and logistic regression models for dichotomous outcomes were estimated to assess differences between groups in the change in either the mean or the odds over time. The models included time as a second-order polynomial, group and the interaction between time and group. A significant interaction term would imply significant between-group differences in change in time. Post hoc analyses were performed to assess within-group changes and between-group differences at each time point. The results of the regression models were tabulated as regression coefficients and standard errors.\u003c/p\u003e \u003cp\u003eBecause surgeries were performed across different time periods, the first year of surgery introduction was used as the index time point. Only one LAP surgery was performed in 2014, and four or fewer OPEN surgeries were performed after 2017; these were excluded from the analyses.\u003c/p\u003e \u003cp\u003eAll statistical analyses were performed in STATA v18. Results with p-values below 0.05 were considered statistically significant. No adjustment for multiple testing was implemented.\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003e\u003cstrong\u003eDemographics\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe study involved 684 patients, with a mean age of 66.5 years (SD 11.6), a mean BMI of 26.2 (SD 4.6), and 38% were women. The OPEN group included n=153 patients; the LAP group, n=341; the ROB group, n=135; and the TaTME group, n=55. Patient characteristics are presented in Table 1. The mean distance from the tumor to the anal verge (AV) was 8.4 cm (SD 3.5) and was shortest in the TaTME group (overall p\u0026lt;0.001 and overall differences were significant between Open and the three other groups (p=0.036 for LAP, p=0.012 for taTME and p=0.039 for ROB). The mean tumor size was 4.3 cm (SD 2.7), which did not differ between the groups. The MRI staging of the tumor (measured in 681 out of 684 cases) showed 26.7% stage I, 42% stage II, 24.4% stage III, and 6.9% stage IV. In the TaTME group, only 18.2% of tumors were stage I and 32.7% were stage III. In the OPEN group, only 31.6% of tumors were stage II and 13.8% stage IV. Overall, between-group differences were significant (p=0.001), but overall differences were significant only for Open vs. LAP (p\u0026lt;0.001) and Open vs. ROB (p=0.020). The need for neoadjuvant systemic treatment was highest in the OPEN group (32.7%) and lowest in the LAP group (24%), with no significant between-group differences.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eImplementation of Minimal Invasive Surgery\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe LAP method was introduced in 2015, and 15 patients were operated on with this procedure the first year. \u0026nbsp;In 2019 and 2020, all but one occurrence included LAP. TaTME was launched in 2015 in collaboration with LAP but recorded only 5 cases that year. It reached 26 cases in 2018 but was discontinued due to national concerns about multifocal local recurrences. (13) The ROB-assisted technique was first performed in 2021on 11 cases. In 2023, ROB was used in 75% cases, rising to 92% by July 2024. Due to enhanced access to the Da Vinci robot, no rectal tumors were treated with LAP in 2024 (Supplemental Table 1).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eIntraoperative complications\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA total of 298 of 398 patients (74.9%) with primary anastomosis received a temporary diverting stoma, which was most common in the TaTME group where all had diverting stoma. The overall conversion rate was 9.4%. It was highest in the LAP group at 13.2% and lowest in the ROB group at only 1.5%.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAll patients with operating time \u0026gt; 268 minutes achieved TO = 1. \u0026nbsp;The overall median operating time was 206 minutes (Q1-Q3 164-259 minutes), 196 minutes in the ROB group, 197 minutes in the OPEN group, 203 minutes in the LAP group and 270 minutes in the TaTME group (overall p\u0026lt;0.001). Still, only the groups OPEN vs. taTME differed significantly (p \u0026lt; 0.001).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eFigure 1A shows the percentage of cases in the study period that operated within the established time limit. According to the logistic regression model (Table 5), there were no significant differences between OPEN and other groups in change in odds of median operating time within 268 minutes, but TaTME group had overall significantly lower odds than the OPEN group (p=0.029). Post hoc analysis suggests no significant trend in the four groups. However, the TaTME group had significantly lower odds of operating time, less than 268 minutes. than the OPEN group at years 1, 2, and 4 (all p=0.009). \u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe total intraoperative complications over the year following the implementation of a new surgical procedure are shown in Figure 1B and Table 2. Eighty percent of TaTME and LAP patients experienced no intraoperative complications during the first year, but this figure dropped to below 75% by the fourth year. The ROB procedure reported no perioperative complications in its first year and remained steady at around 90% in subsequent years. The OPEN procedure had only 10% complications from 2014 to 2017, which increased to about 20% in 2016. According to the logistic regression model (Table 5), there is no difference between OPEN and other groups in change in odds of perioperative complications (no significant interactions between time and operating type) and no overall differences in odds of intraoperative complications.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePostoperative complications\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAccording to Table 3, overall, 20.7% of patients experienced postoperative complications, and there were no significant differences between the groups. 8.3% of patients with an anastomosis experienced an anastomotic leak: OPEN 6.2%, LAP 9.3%, TaTME 11.6%, and ROB 6.2%. \u0026nbsp;87 patients (12.7%) remained in hospital for more than 14 days, with 18% in the OPEN and TaTME groups and 10% in the LAP and ROB groups.\u003c/p\u003e\n\u003cp\u003eFigures 3C show the percentage of TO in achieving no postoperative complications, no LOS over 14 days, and/or readmissions within 30 days. All five TaTME-operated patients in the first year, experienced postoperative complications, but their rates did not differ from those of other groups in subsequent years. According to the logistic regression model (Table 5), there is no difference between the OPEN group and the others in change in odds and no difference in the overall odds for LOS over 14 days. Post hoc analyses revealed no significant trend in the OPEN, LAP, and ROB groups; however, the change in the TaTME group between year 1 and 2 was significant (p=0.049). Moreover, the TaTME group had significantly lower odds of LOS over 14 days than the OPEN group at year 1 (p=0.030).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eOncological outcomes\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe distance from tumor tissue to the CRM is ≤1 mm in 11.4% of cases, the lowest in the ROB group at 8.9% and highest in the TaTME group with 21.8% (overall p=0.014 with no significant overall differences).\u003c/p\u003e\n\u003cp\u003eAccording to Quirke, the mesorectum is either complete or nearly complete in 85.7% of cases, demonstrating the best performance in the ROB group (88.9%) and underperforming in the TaTME group (67.3%; overall p\u0026lt;0.001 and the only significant overall difference between OPEN and taTME, p=0.008). The distance from the distal resection (DR) to tumor tissue was ≤1 mm in only 2 cases: 1 in the TaTME group and 1 in the ROB group. In 92.5% of cases, the specimen contained at least 12 lymph nodes (Table 4).\u003c/p\u003e\n\u003cp\u003eFigure 1D illustrates the percentage of TOs related to oncological quality. According to the logistic regression model (Table 5), there is no difference between OPEN and other groups in the change in the odds and in the overall odds of no oncological adverse outcome.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTextbook outcome\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA TO was achieved in 38% of all the patients in this study. When combined with all cases achieving near complete TO (≥7), the total rises to 66.2%. In 5.6% of cases, the score was below five on the TO scale. Even in the well-established OPEN group, the TO rate did not exceed 32% over the 4 years. However, the ROB group (37.8%) and the LAP group (36.3%) had better average TO rates. The TaTME group had only an average TO of 22%, and during the first year with TaTME, none of the patients achieved TO. Nonetheless, over the following three years, the method stabilized a TO between 55% and 59% (Figures 2 and 3). \u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe distribution of TO points during the first four years differed across surgical approaches (Figure 4). In Years 1 and 2, robotic and laparoscopic TME had a higher proportion of patients achieving ≥7 TO points than open surgery and TaTME. Robotic TME showed the most consistent performance across all four years, with a steady proportion of patients reaching the highest TO category (≥7 points).\u003c/p\u003e\n\u003cp\u003eTaTME exhibited a distinct early learning-curve pattern, characterized by a higher proportion of patients with \u0026lt;5 TO points in Year 1 and an absence of patients achieving ≥7 TO points. Performance improved progressively over subsequent years, with a larger proportion of patients reaching higher TO categories by Years 3 and 4. Open surgery demonstrated intermediate performance, with gradual improvement over time but greater variability than laparoscopic and robotic approaches.\u003c/p\u003e\n\u003cp\u003eAccording to the linear regression model (Table 5), the change in the TaTME group differs significantly from that in the OPEN group (p=0.002 and p=0.006 for the interaction between time and operation type).\u0026nbsp;\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eIn this study, we have demonstrated that, compared to the gold standard of open surgery, laparoscopic and robotic surgery achieved acceptable quality measures and TO during the early learning curve. Conversely, this study indicates that TaTME has experienced performance issues related to skin-to-skin operating time, increased length of stay, and readmissions, and, overall, shows poor performance with respect to TO.\u003c/p\u003e \u003cdiv id=\"Sec19\" class=\"Section2\"\u003e \u003ch2\u003eResearch in context\u003c/h2\u003e \u003cp\u003eOur study aligns with other studies related to the TO. Warps et al. conducted a study to evaluate TO after rectal cancer surgery as a short-term quality-of-care measure. Patients who underwent rectal cancer surgery between 2012 and 2019 were included. TO was defined as being alive at 30 days or during the primary admission, without reinfection, complications, or readmission, with a hospital stay of no more than 14 days and having tumor-free margins. 56.3% achieved TO and concluded that postoperative complications mainly influence rectal cancer outcomes. In their view, TO does not align with the plan-do-check-act cycle of clinical auditing. They also believed that TO adds little value to current outcome indicators for rectal cancer surgery. (\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e)\u003c/p\u003e \u003cp\u003eMac Curtain et al. conducted a systematic review of 15 studies involving 301,502 patients and found that TO was achieved in an average of 55% of reported cases. The paper concluded that there is no standardized definition of TO in use, and that a Delphi consensus is warranted to enable meaningful comparisons using TO in the future. (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e)\u003c/p\u003e \u003cp\u003eArrighini et al concluded in their paper that TO is an effective indicator for assessing the quality of colorectal cancer surgery. By standardizing TO parameters, they believe the consistency and quality of care across institutions can be enhanced. The authors suggest a unified definition of TO for colorectal surgery: radical resection, LN yield\u0026thinsp;\u0026ge;\u0026thinsp;12, no Clavien-Dindo\u0026thinsp;\u0026ge;\u0026thinsp;III, length of stay (75th percentile), no 30-day readmissions, and no 30-day mortality. (\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e)\u003c/p\u003e \u003cp\u003eThese studies use TO to compare colorectal cancer care across different institutions, rather than to analyze intra-hospital early learning curves for minimally invasive rectal cancer surgery. The higher number of TO variables in our study (n\u0026thinsp;=\u0026thinsp;8) might explain why the TO rate here is lower than reported in other studies.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec20\" class=\"Section2\"\u003e \u003ch2\u003eOncological outcomes\u003c/h2\u003e \u003cp\u003eIn previous studies assessing TO, the quality of the mesorectum is not included in the TO assessment. Without this variable, the total percentage of a \u0026ldquo;perfect oncological outcome\u0026rdquo; rises from 72\u0026ndash;82%, and the total number of TO rises to 38.7%.\u003c/p\u003e \u003cp\u003eThe overall numbers with near complete TO (\u0026ge;\u0026thinsp;7 points) are 64% in OPEN group, 65.9% in the ROB group, 67% LAP group 1\u0026ndash;4, and 73.8% LAP group 5\u0026ndash;9. On the other hand, the TaTME group are significantly lower with only 38.9% This supports the importance of including oncological outcomes to obtain comparable values for TO.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec21\" class=\"Section2\"\u003e \u003ch2\u003eOperating time\u003c/h2\u003e \u003cp\u003eOperating time during the implementation of a new surgical procedure may be longer than that for established techniques. This is why operating time is treated as a variable in this study and in all surgical learning-curve studies. We observed no significant differences between the OPEN and other groups, except for TaTME, in overall odds for operating time within 268 minutes (median time\u0026thinsp;+\u0026thinsp;30%).\u003c/p\u003e \u003cp\u003eTaTME is a challenging surgery performed by two teams and remains difficult despite mentorship and global training. The TaTME approach was only used for patients with rectal cancer less than 10 cm from the anal margin, resulting in longer dissection times than for other groups also including high rectal tumors. TaTME use was discontinued after 55 cases, but the steep learning curve suggests that, by 100 cases, operating time could be comparable to that of other procedures.\u003c/p\u003e \u003cp\u003eThe initial 30 robotic-assisted rectal surgery operations were limited to women with low, mid, and high rectal cancer and men with high rectal cancer, excluding neoadjuvant-treated patients. Due to successful procedures, these exclusion criteria were lifted after 15 cases. No exclusion criteria were used when we started laparoscopic rectal cancer treatment. Still, the first 15 LAP patients (year 1) had a higher TO\u0026thinsp;=\u0026thinsp;1 score for operating time than the other groups. This is challenging to explain, yet 40 of 60 patients that year underwent open surgery, suggesting that more complex cases were selected. However, except in the TaTME group, novel rectal surgical approaches have not considerably extended operating time throughout the learning curve.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec22\" class=\"Section2\"\u003e \u003ch2\u003eIntraoperative complications\u003c/h2\u003e \u003cp\u003eThe TO score shows that the TaTME group did not differ significantly from the other groups across the four years regarding intraoperative complications. According to ClassIntra classification, the TaTME group experienced five (45%) grade 3 complications, including two severe urethral injuries, a well-known complication associated with the trans anal approach.\u003c/p\u003e \u003cp\u003eThe robotic group experienced no intraoperative complications out of the 11 cases in the first year and scored 1 point due to TO in about 90% of cases across the four first years. The overall perioperative complication rate for the ROB group is 9.6% (the lowest of all groups), but 10 out of 13 perioperative complications (76.9%) are classified as Grade 3.\u003c/p\u003e \u003cp\u003ePost hoc analyses show that in the second year, the LAP group has significantly lower odds of perioperative complications than the OPEN group.\u003c/p\u003e \u003cdiv id=\"Sec23\" class=\"Section3\"\u003e \u003ch2\u003ePostoperative complications\u003c/h2\u003e \u003cp\u003eAt year 1, all five patients with TaTME experienced postoperative complications, with odds significantly different from the OPEN group (p\u0026thinsp;=\u0026thinsp;0.030). By year 2, approximately 65% of the TaTME group scored on the TO scale. The ROB group had the lowest percentage of LOS\u0026thinsp;\u0026ge;\u0026thinsp;14 days (9.6%); however, it also had the highest readmission rate (28.1%), compared with OPEN (19%) and LAP (17.3%). One possible reason for this could be early discharges from hospital within the ROB group and a higher incidence of presacral abscesses that were not diagnosed during the initial hospitalization.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec24\" class=\"Section2\"\u003e \u003ch2\u003eLimitations\u003c/h2\u003e \u003cp\u003eLimitations exist. This is a retrospective study, and patient selection for each surgical procedure depended on the availability of skilled surgeons and robots, the patients\u0026rsquo; BMI (obesity, narrow pelvis), previous abdominal surgery, and comorbidities.\u003c/p\u003e \u003cp\u003ePatients without complications, with a LOS of less than 14 days, and who are not readmitted within 30 days achieve TO. Conversely, a patient with a postoperative complication, who remains in hospital for more than 14 days or is readmitted within 30 days, will unlikely achieve TO\u0026thinsp;\u0026ge;\u0026thinsp;7 due to one complication. This may introduce bias into the study and supports the conclusion of the Warp review article.(\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e)\u003c/p\u003e \u003cp\u003eThe number of mobilizations of the splenic flexure varies across the four groups: 25 (16.3%) in the OPEN group, 202 (59.2%) in the LAP group, 78 (57.8%) in the ROB group, and 47 (85.5%) in the TaTME group. It generally takes about 30 to 60 minutes to mobilize the splenic flexure. This paper does not account for this because the operating description does not specify precisely how long it took to mobilize the left flexure.\u003c/p\u003e \u003cp\u003eThis study does not distinguish between high and low anterior resection, which is a limitation because the TaTME group includes only low rectal cancers (below 10cm from AV). The reasons for including high rectal cancers are the relatively small number of these cancers diagnosed each year and the fact that most surgical steps are similar in high and low rectal cancer procedures. In the TaTME group, there are significantly more cases with anastomosis than in the other groups, leading to a higher risk of anastomosis-related complications.\u003c/p\u003e \u003cp\u003eSince TaTME involves both an abdominal and a transanal approach, with the latter being relatively unfamiliar to surgeons, the skin-to-skin operating time is longer. This, combined with only 5 cases in the first year, an overall lower tumor stage, a notably higher number of anastomoses, and the fact that the procedure was cancelled after 55 cases, makes it difficult to determine whether it would have been possible to achieve the same TO as the LAP and ROB groups after approximately 100\u0026ndash;150 cases.(\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e)\u003c/p\u003e \u003cdiv id=\"Sec25\" class=\"Section3\"\u003e \u003ch2\u003eStrengths\u003c/h2\u003e \u003cp\u003eThe study relies on a meticulously collected quality registry spanning 10 years, which enables the assessment of the implementation and early learning curve of three minimally invasive rectal cancer surgery methods. To our knowledge, this has not been done by others, thereby enhancing the study's uniqueness.\u003c/p\u003e \u003cp\u003eFour surgeons at the hospital performed most of the minimally invasive surgical procedures. This suggests that, when transitioning from laparoscopic to robot-assisted surgery, these five surgeons were well trained in minimally invasive rectal surgery, which likely steepened the learning curve and provided acceptable TO.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e"},{"header":"Conclusions","content":"\u003cp\u003eFor surgical departments, it is crucial not only to analyze TO during the early learning curve of minimally invasive rectal cancer surgery but also to conduct a detailed examination of quality measures, including operating time, perioperative complications, postoperative events, and oncological outcomes. Regular intrahospital quality control of these parameters during MIS implementation will ensure surgical work is of satisfactory quality or identify aspects of the surgical procedure that need adjustment to achieve better results.\u003c/p\u003e \u003cp\u003eDuring the early learning curve, TaTME encountered performance challenges, whereas laparoscopic and robotic TME showed positive initial learning curve results. The TO can serve as a standardized in-hospital benchmark for assessing the quality of the early learning curve.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgements:\u0026nbsp;\u003c/strong\u003eWe thank all operating surgeons and RN at the CRC team at the Department of Gastrointestinal Surgery, Akershus University Hospital.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contribution\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eRolf Riis: Conceptualization, Methodology, Validation, Investigation, Data Curation, Writing – Original Draft, Writing – Review\u003c/p\u003e\n\u003cp\u003eKnut Magne Augestad: Conceptualization, Methodology, Validation, Investigation, Writing – Original Draft, Writing – Review, Supervision, Funding.\u003c/p\u003e\n\u003cp\u003eJūratė Šaltytė Benth: Methodology, Software, Validation, Formal Analysis, Investigation, Visualisation, Supervison.\u003c/p\u003e\n\u003cp\u003eMargit Riis: Data Curation, Writing – Original Draft; Writing -Review, Analyses, Visualisation.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding:\u003c/strong\u003e This research was funded by a grant from the Division of Surgery, Akershus University Hospital, Lørenskog, Norway.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData sharing:\u003c/strong\u003e Under Norwegian law, data sharing is not permitted.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eMac Curtain BM, Qian W, O\u0026apos;Mahony A, Deshwal A, Mac Curtain RD, Temperley HC, et al. \u0026quot;Textbook outcome(s)\u0026quot; in colorectal surgery: a systematic review and meta-analysis. Ir J Med Sci. 2024;193(5):2187\u0026ndash;94.\u003c/li\u003e\n\u003cli\u003eAly M, Chang Y-H, Stucky C-C, Fong ZV, Etzioni D, Wasif N. Long-Term Survival After Surgical Resection for Rectal Cancer Is Associated With Textbook Outcome but Not Surgical Case Volume. Annals of Surgery Open. 2025;6(3).\u003c/li\u003e\n\u003cli\u003eSofia S, Degiuli M, Anania G, Baiocchi GL, Baldari L, Baldazzi G, et al. Textbook Outcome in Colorectal Surgery for Cancer: An Italian Version. J Clin Med. 2024;13(16).\u003c/li\u003e\n\u003cli\u003eGupta V, Mor A, Mundhada RO, Kazi MK, Daphal AJ, Sharma A, et al. Textbook Outcomes of Minimally Invasive Total Mesorectal Excision: A Composite Tool to Assess and Compare Outcomes for Benchmarking. Dis Colon Rectum. 2025;68(9):1042\u0026ndash;51.\u003c/li\u003e\n\u003cli\u003eSun Y, Tang Z, Jiang W, Wang X, Huang Y, Chi P. Textbook outcome in low rectal cancer patients undergoing laparoscopic or open surgery: 3-year results from the multicentric LASRE Trial. Int J Colorectal Dis. 2025;40(1):177.\u003c/li\u003e\n\u003cli\u003eDincler S, Koller MT, Steurer J, Bachmann LM, Christen D, Buchmann P. Multidimensional analysis of learning curves in laparoscopic sigmoid resection: eight-year results. Dis Colon Rectum. 2003;46(10):1371\u0026ndash;8; discussion 8\u0026ndash;9.\u003c/li\u003e\n\u003cli\u003eTekkis PP, Senagore AJ, Delaney CP, Fazio VW. Evaluation of the learning curve in laparoscopic colorectal surgery: comparison of right-sided and left-sided resections. Ann Surg. 2005;242(1):83\u0026ndash;91.\u003c/li\u003e\n\u003cli\u003eM\u0026uuml;ller PC, Kuemmerli C, Cizmic A, Sinz S, Probst P, de Santibanes M, et al. Learning Curves in Open, Laparoscopic, and Robotic Pancreatic Surgery. Annals of Surgery Open. 2022;3(1).\u003c/li\u003e\n\u003cli\u003eKim CH, Kim HJ, Huh JW, Kim YJ, Kim HR. Learning curve of laparoscopic low anterior resection in terms of local recurrence. J Surg Oncol. 2014;110(8):989\u0026ndash;96.\u003c/li\u003e\n\u003cli\u003eBurghgraef TA, Sikkenk DJ, Verheijen PM, Moumni ME, Hompes R, Consten ECJ. The learning curve of laparoscopic, robot-assisted and transanal total mesorectal excisions: a systematic review. Surg Endosc. 2022;36(9):6337\u0026ndash;60.\u003c/li\u003e\n\u003cli\u003eLau SYC, Choy KT, Yang TWW, Heriot A, Warrier SK, Guest GD, et al. Defining the learning curve of transanal total mesorectal excision: a systematic review and meta-analysis. ANZ J Surg. 2022;92(3):355\u0026ndash;64.\u003c/li\u003e\n\u003cli\u003eGachabayov M, You K, Kim SH, Yamaguchi T, Jimenez-Rodriguez R, Kuo LJ, et al. Meta-Analysis of the Impact of the Learning Curve in Robotic Rectal Cancer Surgery on Histopathologic Outcomes. Surg Technol Int. 2019;34:139\u0026ndash;55.\u003c/li\u003e\n\u003cli\u003eRiis RN, Riis MH, Benth JS, Augestad KM. Beyond the transanal total mesorectal excision moratorium: local and distant recurrence among patients operated for low rectal tumors-5-year follow-up from a Norwegian University Hospital. Br J Surg. 2023.\u003c/li\u003e\n\u003cli\u003eDell-Kuster S, Gomes NV, Gawria L, Aghlmandi S, Aduse-Poku M, Bissett I, et al. Prospective validation of classification of intraoperative adverse events (ClassIntra): international, multicentre cohort study. BMJ. 2020;370:m2917.\u003c/li\u003e\n\u003cli\u003eClavien PA, Barkun J, de Oliveira ML, Vauthey JN, Dindo D, Schulick RD, et al. The Clavien-Dindo classification of surgical complications: five-year experience. Ann Surg. 2009;250(2):187\u0026ndash;96.\u003c/li\u003e\n\u003cli\u003eDindo D, Demartines N, Clavien PA. Classification of surgical complications: a new proposal with evaluation in a cohort of 6336 patients and results of a survey. Ann Surg. 2004;240(2):205\u0026ndash;13.\u003c/li\u003e\n\u003cli\u003eWarps AK, Detering R, Tollenaar R, Tanis PJ, Dekker JWT, Dutch ColoRectal Audit g. Textbook outcome after rectal cancer surgery as a composite measure for quality of care: A population-based study. Eur J Surg Oncol. 2021.\u003c/li\u003e\n\u003cli\u003eArrighini GS, Martinino A, Zecchin Ferrara V, Lorenzon L, Giovinazzo F. Textbook oncologic outcomes in colorectal cancer surgery: a systematic review. Frontiers in Oncology. 2025;15.\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Tables","content":"\u003cp\u003eTables 1 to 5 are available in the Supplementary Files section.\u003c/p\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-8507148/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8507148/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eAim\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe Textbook Outcome (TO) is a valuable tool for benchmarking but has not been used to evaluate the early learning curve of minimally invasive rectal cancer surgery. This retrospective study compared TO over a 10-year period across four surgical approaches to TME—open surgery (OPEN), laparoscopic (LAP), transanal (TaTME), and robotic (ROB)—focusing on the early learning-curve phase.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMethods\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe examined 684 patients who underwent minimally invasive rectal cancer surgery from January 2014 to July 2024. TO was defined using an 8-point scoring system assessing operating time deviation, intraoperative complications (ClassIntra), postoperative complications (Clavien-Dindo III-V), length of stay \u0026gt;14 days or readmission within 30 days, mesorectal completeness, CRM ≤1mm, distal resection margin ≤1mm, lymph node harvest \u0026lt;12. Regression analysis was used to compare early learning curves in TO across surgical approaches.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003ePatient demographics were similar across the OPEN (n=153), LAP (n=341), TaTME (n=54), and ROB (n=135) groups. ROB demonstrated consistent TO ratings from the beginning, the shortest average operating time (208 min, SD 60, overall p\u0026lt;0.001), and the lowest rate of perioperative complications (overall p=0.013). Overall, there were no significant differences among the groups regarding postoperative complications. The highest quality of mesorectal excision was observed in the robotic group (TaTME: 67.3%; OPEN: 84.6%; LAP: 87.9%; ROB: 88.9%; overall p\u0026lt;0.001). TaTME experienced early learning curve challenges in achieving TO, with first year cases showing a higher postoperative complication rate (overall p=0.030) and no TaTME cases meeting operating-time targets in the first year (overall p=0.029), although this improved within two years.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusion\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eDuring the early learning phase, TaTME faced performance challenges, whereas laparoscopic and robotic TME implementation showed positive initial learning-curve results. The TO can serve as a standardized benchmark for assessing the quality of the early learning curve. Conducting regular intrahospital quality control of TO will verify whether the surgical work is of satisfactory quality or identify any aspects of the surgical procedure that need adjustment to achieve better results.\u003c/p\u003e","manuscriptTitle":"Benchmarking the Learning Curve of Minimally Invasive Rectal Cancer Surgery Using Textbook Outcome: A Retrospective Analysis of Laparoscopic, Robotic, and Transanal Rectal Cancer Resections","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-01-16 09:15:12","doi":"10.21203/rs.3.rs-8507148/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":"fdd6cfe2-50ff-4070-b5f7-85aeb27af891","owner":[],"postedDate":"January 16th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-03-13T11:10:46+00:00","versionOfRecord":[],"versionCreatedAt":"2026-01-16 09:15:12","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8507148","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8507148","identity":"rs-8507148","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}