Assessing the learning curve of robot-assisted total mesorectal excision: a multicenter study considering procedural safety, pathological safety, and efficiency

International Journal of Colorectal Disease https://doi.org/10.1007/s00384-022-04303-7 (2023) 38:9 RESEARCH Assessing the learning curve of robot‑assisted total mesorectal excision: a multicenter study considering procedural safety, pathological safety, and efficiency T. A. Burghgraef1,2 · D. J. Sikkenk2 · R. M. P. H. Crolla3 · M. Fahim4 · J. Melenhorst5 · M. El Moumni1 · G. van der Schelling3 · A. B. Smits4 · L. P. S. Stassen5 · P. M. Verheijen2 · E. C. J. Consten1,2 Accepted: 7 December 2022 © The Author(s) 2023 Abstract Purpose Evidence regarding the learning curve of robot-assisted total mesorectal excision is scarce and of low quality. Casemix is mostly not taken into account, and learning curves are based on operative time, while preferably clinical outcomes and literature-based limits should be used. Therefore, this study aims to assess the learning curve of robot-assisted total mesorectal excision. Methods A retrospective study was performed in four Dutch centers. The primary aim was to assess the safety of the individual and institutional learning curves using a RA-CUSUM analysis based on intraoperative complications, major postoperative complications, and compound pathological outcome (positive circumferential margin or incomplete TME specimen). The learning curve for efficiency was assessed using a LC-CUSUM analysis for operative time. Outcomes of patients before and after the learning curve were compared. Results In this study, seven participating surgeons performed robot-assisted total mesorectal excisions in 531 patients. Learning curves for intraoperative complications, postoperative complications, and compound pathological outcome did not exceed predefined literature-based limits. The LC-CUSUM for operative time showed lengths of the learning curve ranging from 12 to 35 cases. Intraoperative, postoperative, and pathological outcomes did not differ between patients operated during and after the learning curve. Conclusion The learning curve of robot-assisted total mesorectal excision based on intraoperative complications, postoperative complications, and compound pathological outcome did not exceed predefined limits and is therefore suggested to be safe. Using operative time as a surrogate for efficiency, the learning curve is estimated to be between 12 and 35 procedures. Keywords Robot-assisted surgery · Rectal cancer · Total mesorectal excision · Learning curve Introduction * T. A. Burghgraef 1 Department of Surgery, University Medical Centre Groningen, Groningen, The Netherlands 2 Department of Surgery, Meander Medical Centre, Amersfoort, The Netherlands 3 Department of Surgery, Amphia Hospital, Breda, The Netherlands 4 Department of Surgery, St Antonius Hospital, Nieuwegein, The Netherlands 5 Department of Surgery, Maastricht University Medical Centre, Maastricht, The Netherlands Surgical resection is the cornerstone of rectal cancer treatment. This is performed according to the total mesorectal excision (TME) principle, using minimally invasive approaches such as laparoscopic (L-TME), robot-assisted (R-TME) or transanal (TaTME) [1]. Multiple papers have compared L-TME with R-TME and TaTME [2]. If performed by experienced surgeons, R-TME and TaTME may result in an increased primary anastomosis rate, although no difference in postoperative or oncological outcome has been found [3–6]. However, outcomes of minimally invasive surgery are suggested to be influenced by the learning curve [5]. Current literature regarding learning curves of L-TME, 13 Vol.:(0123456789) 9 Page 2 of 12 R-TME, and TaTME suggests that the length of the learning curve of R-TME is comparable with TaTME and L-TME [7–11]. However, increased intraoperative complication rates and local recurrence rates were seen during the learning curve of TaTME in the Netherlands and Norway [12–14]. This has led to an increase in studies evaluating the learning curve of TaTME and R-TME. Despite the increased number of papers published on this topic, studies are mostly of poor quality. Series are small and use different definitions for rectal carcinoma, or even include rectal resections for benign diseases as well. Additionally, different outcomes and statistical methods are used to assess the learning curve [15–22]. Mostly, solely operating time is used for assessing the learning curve, without considering clinical outcomes, while the latter are said to be a better surrogate for the learning curve [23]. Additionally, if an appropriate statistical analysis is used, adjusting for case-mix is mostly not done, and length of the learning curve is based on averages of the series (hence, intersurgeons’ differences were measured) instead of using literature-based limits. Therefore, this study aimed to assess the learning curve of R-TME using clinical outcomes primarily, by means of RA-CUSUM analyses using literature-based limits. Methods This is a retrospective multicenter cohort to assess the learning curve of R-TME in four large Dutch teaching hospitals. Learning curves will be assessed for individual surgeons and institutions. A protocol regarding the data-analysis was composed prior to initiation of the study. The manuscript was written according to the STROBE guidelines [24]. Design This study involves four robot-assisted centres using the da Vinci system (Intuitive Systems, Sunnyvale, CA, USA). None of the surgeons had prior experience with robotassisted surgery, and start of the R-TME was preceded by electronic training, animal training, and proctoring of the first 5 procedures led by Intuitive. All surgeons had profound experience with more than 200 L-TMEs and more than 100 open TME procedures performed per surgeon. Centers started with the technique between 2011 and 2016. In the center, the A cases were operated using the DaVinci Xi, performed by one dedicated surgeon. Center B and C used the DaVinci Si, performed by two dedicated surgeons and a dedicated team of OR nurses per center. Center D used the DaVinci Xi, performed by two dedicated surgeons. 13 International Journal of Colorectal Disease (2023) 38:9 Patients All consecutive patients that underwent R-TME since its introduction in the specific center were included if they met the following criteria: (1) in need of TME, (2) diagnosed with rectal cancer according to the Sigmoid take-off definition [25], (3) were 18 years or older, (4) were operated in an elective setting with (5) curative intent, and (6) if the performing surgeon had performed > 20 cases during the inclusion period. There were no predefined exclusion criteria. All preoperative decisions and postoperative followup were in accordance with the Dutch guideline colorectal carcinoma [26]. Outcomes Our primary outcome was to assess the learning curve of the individual surgeons using clinical outcomes. The used clinical outcomes were as follows: intraoperative complications, postoperative major morbidity, and compound pathological outcome. Intraoperative c (...truncated)