Learning Curve of Endoscopic Nipple-Sparing Mastectomy: A Single-Surgeon CUSUM Analysis of 62 Consecutive Cases

초록

Background: Nipple-sparing mastectomy (NSM) with immediate reconstruction has become a widely accepted surgical option for patients seeking oncologic safety and cosmetic preservation. With the introduction of endoscopic nipple-sparing mastectomy (ENSM), minimally invasive approaches have evolved to reduce incision size and improve aesthetic outcomes. However, evidence regarding the learning process and technical maturation of ENSM remains limited. This study aimed to evaluate the learning curve of ENSM performed by a single surgeon using cumulative sum (CUSUM) analysis. Methods: Between April 2024 and October 2025, a total of 100 patients underwent ENSM with immediate reconstruction at Korea University Ansan Hospital. Among them, 74 cases were performed by a single surgeon (H.Y. Lee), and 62 consecutive cases without axillary lymph node dissection (ALND) were included in the learning curve analysis. The mastectomy operative time was defined as the duration of the endoscopic dissection phase. Learning curve evaluation was performed using CUSUM analysis, and three phases were identified according to changes in the slope: learning (cases 1–8), transition (cases 9–30), and plateau (≥31). Differences in operative time across phases were analyzed using one-way ANOVA. Results: A total of 74 patients underwent endoscopic nipple-sparing mastectomy (ENSM) with immediate reconstruction between April 2024 and October 2025. The mean age of the patients was 50.3 ± 7.5 years, and the mean body mass index (BMI) was 24.3 ± 3.3 kg/m². The average breast specimen weight was 341.2 ± 139.5 g.The mean operative time decreased significantly as the number of cases increased: 180.6 ± 40.9 minutes during the learning phase, 149.7 ± 31.1 minutes during the transition phase, and 119.7 ± 28.1 minutes during the plateau phase (p < 0.001). The CUSUM curve reached its peak at the 8th case and stabilized after approximately 30 cases, indicating the acquisition of technical proficiency and surgical efficiency. Conclusion: The learning curve of endoscopic nipple-sparing mastectomy demonstrates a clear reduction in operative time and stabilization after approximately 30 cases. This single-surgeon experience provides quantitative insight into the learning process of ENSM and underscores the importance of structured training and case accumulation during early adoption to achieve proficiency and consistent outcomes. No conflict of interest