Learning curve analysis for prophylactic bilateral robot-assisted lateral lymph node dissection for lower rectal cancer: a retrospective study

Background Lateral lymph node dissection (LLND) is an important surgical procedure in the treatment of lower rectal cancer (RC). However, limited data are available regarding the learning curve for robot-assisted LLND (RA-LLND). This study aimed to evaluate the learning curve for prophylactic bilateral RA-LLND for lower RC. Methods We retrospectively analyzed 58 consecutive patients with clinical stage II/III lower RC who had undergone prophylactic bilateral RA-LLND between July 2020 and June 2024. Cumulative sum (CUSUM) analysis was used to evaluate the learning curve for bilateral RA-LLND operative time. Results The mean age of patients was 61.5 years, and mean body mass index was 23.4 kg/m(2). The proportion of neoadjuvant therapy was 8.6%. Mean prophylactic bilateral RA-LLND operative time was 173.7 min. CUSUM analysis divided the learning curve for prophylactic bilateral RA-LLND operative time into three phases: initial learning phase (20 cases); competence phase (16 cases); and master/proficiency phase (subsequent cases). Mastery of surgical technique was achieved after performing the 36th case. Comparisons of surgical outcomes in terms of operative parameters and complications were made between phases 1 and 2 combined and phase 3. A significant reduction in mean prophylactic bilateral RA-LLND operative time was observed between phases 1 and 2 compared with phase 3 (P < 0.01). Mean blood loss was decreased in phase 3 (40.5 ml) compared to phases 1 and 2 combined (148.2 ml, P < 0.01). The frequencies of overall postoperative complications directly related to LLND and urinary dysfunction were significantly reduced in phase 3 compared to phases 1 and 2 combined (P = 0.04, and P = 0.02, respectively). Conclusions The three phases identified by CUSUM analysis represented characteristics of the learning curve for prophylactic bilateral RA-LLND. These data suggest that 20 cases are required for the early stage of the learning curve, whereas mastery level could be achieved after 36 cases.