Learning curve analysis of extraperitoneal single-site robotic-assisted radical prostatectomy: a CUSUM-based approach

This study applied cumulative sum (CUSUM) analysis to evaluate trends in operative time and blood loss, It aims to identify key milestones in mastering extraperitoneal single-site robotic-assisted radical prostatectomy (ss-RARP). A cohort of 100 patients who underwent ss-RARP, performed by a single surgeon at the First Affiliated Hospital of Guangzhou Medical University between March 2021 and June 2023, was retrospectively analyzed. To evaluate the learning curve, the CUSUM (Cumulative Sum Control Chart) technique was applied, revealing the progression and variability over time. A cubic polynomial model was utilised to fit the non-linear data trends accurately. Key perioperative outcomes, such as operative duration and estimated blood loss, were assessed and compared between distinct learning stages to identify improvements and transitions during the surgeon's proficiency development. A total of 100 patients were included, with a mean age of 71.44 ± 5.46 years. The median operative time was 119.53 min (94, 144), and the best-fit equation for the CUSUM learning curve of operative time was y = 387.0373 - 3.4334x - 0.2982x² + 0.003x³ (R² = 0.898), reaching its peak at the 11th case. The median blood loss was 49.9 ml (20, 50), and the best-fit equation for the CUSUM learning curve of blood loss was y = 444.9362 + 23.6787x - 0.7719x² + 0.0049x³ (R² = 0.957), reaching its peak at the 27th case. The learning curve was divided into a learning phase (1-27 cases) and a proficient phase (28 cases onward). Intraoperative blood loss significantly decreased from 75.93 ± 79.19 mL to 40.27 ± 35.27 mL in the proficient phase (P < 0.05), while operative time remained similar between phases (P > 0.05).There were no statistically significant differences in pelvic drainage tube placement time, drainage volume, positive surgical margin rate, hospital stay duration, or postoperative pain scores (P > 0.05). The findings suggest that proficiency in ss-RARP is typically achieved after approximately 27 cases, indicating a manageable and safe learning curve. These insights can inform the design of surgical training programmes, optimising early learning and improving clinical outcomes for novice surgeons.