Learning process analysis of robotic lateral pelvic lymph node dissection for local advanced rectal cancer: the CUSUM curve of 78 consecutive patients

Robotic lateral lymph node dissection (LLND) has been described as a safe and feasible procedure for local advanced rectal cancer. The aim of this study was to evaluate the learning curve for robotic-assisted LLND. We collected data on 78 consecutive patients who underwent robotic-LLND at our hospital. The learning curve was analyzed using the cumulative sum (CUSUM) method to assess changes in the unilateral LLND operative times across the case sequence. Among the 78 patients, 52 underwent bilateral LLND and 26 underwent unilateral LLND. A total of 130 consecutive data were recorded. We arranged unilateral robotic-LLND operative times and calculated cumulative sum values, allowing the differentiation of three phases: phase I (learning period, cases 1–51); phase II (proficiency period, cases 52–83); and phase III (mastery period, cases 84–130). As the learning curve accumulated, the operation time and estimated blood loss of unilateral robotic-LLND decreased significantly with each phase (P < 0.05). By 12 months after surgery, the International Prostatic Symptom Score of patients at phase III was significantly lower than at phase I (P < 0.05). The CUSUM curve shows three phases in the learning of robotic-LLND. The estimated learning curve for robotic-assisted rectal-LLND is achieved after 51 cases.