Short- and long-term impact of the TaTME learning process: a single institutional study.

Background: Transanal total mesorectal excision (TaTME) is a promising and innovative approach for lower rectal cancer but requires high technical skill and learning process that can affect patient outcomes. We aimed to determine the learning curve of TaTME and then to assess its impact on 5-year oncologic outcomes.

Methods: Over a 54-month period, 94 patients underwent TaTME by experienced laparoscopic colorectal surgeons at our department. To provide a comprehensive overview of success, we used a composite criterion including the most relevant parameters related to the learning process: the conversion rate to an open procedure, TaTME procedure completion, severe postoperative morbidity, mesorectal integrity on macroscopic evaluation, and microscopic margins. Moving average method and cumulative sum analyses were performed.

Results: The operative time continuously decreased over the entire study period. The success rate stabilised after 14 patients in a parallel and balanced analysis of the two surgeons' experiences. Mesorectal completeness was the most sensitive marker for the TaTME learning process (42.9% vs 71.25%; p = 0.06). The learning process did not significantly affect the postoperative morbidity, conversion rate, or R0 resection. Five-year oncological outcomes were similar between the groups.

Conclusion: Even among laparoscopically experienced surgeons, the TaTME learning process influences the oncological quality of the resection but not the postoperative morbidity. Gaining an early command of the surgical anatomy and technical skills and understanding the challenges through specific educational sessions are necessary. The results of this study could help generate a comprehensive training program and define necessary prerequisites for prospective trials.

Trial registration: This study is registered in our Clinical Research Unit (2016_LELONG_01). Our database is registered in the clinicalTrials.gov registry: Institut Paoli Calmettes Colorectal Cancer Database (NCT02869503).