Learning Curve of Robotic Rectal Surgery Using Risk-Adjusted Cumulative Summation: A Five-Year Institutional Experience

Purpose: We delineated the learning phases of robot-assisted laparoscopic surgery for rectal cancer and compared the surgical and clinical outcomes between robot-assisted laparoscopic surgery and conventional laparoscopic surgery. Methods In total, 210 patients underwent rectal cancer surgery at Sendai Medical Center from 2015 to 2020. Conventional laparoscopic surgery was performed in 110 patients, while robot-assisted laparoscopic surgery was performed in 100 patients. The learning curve was evaluated using the cumulative summation method, risk-adjusted cumulative summation method, and logistic regression analysis. Results The risk-adjusted cumulative summation learning curve was divided into three phases: phase 1 (cases 1–48), phase 2 (cases 49–80), and phase 3 (cases 81–100). The length of hospital stay (13.1 days vs. 18.0 days, respectively; p = 0.016) and the surgical duration (209.1 minutes vs. 249.5 minutes, respectively; p = 0.045) were significantly shorter in the robot-assisted laparoscopic surgery group (phase 3) than in the conventional laparoscopic surgery group. The volume of blood loss was significantly lower in the robot-assisted laparoscopic surgery group (phase 1) than in the conventional laparoscopic surgery group (17.7 ml vs. 79.7 ml, respectively; p = 0.036). The International Prostate Symptom Score was significantly lower (indicating less severe symptoms) in the robot-assisted laparoscopic surgery group (p = 0.0131). Conclusions Robot-assisted laparoscopic surgery for rectal cancer was safe and demonstrated better surgical and clinical outcomes, including a shorter hospital stay, less blood loss, and a shorter surgical duration, than conventional laparoscopic surgery. Tactile familiarity can be acquired from visual information beyond 80 cases.