Learning curve for total gastrectomy with D2 lymph node dissection: Cumulative sum analysis for qualified surgery

Background: This study was conducted to evaluate the leaning curve of D2 lymph node dissection for patients with gastric cancer in a high-volume center. Methods: The authors prospectively reviewed the data of all patients who underwent total gastrectomy with D2 lymph node dissection during a 4-year period. Retrieved lymph node number was used as a surrogate marker of oncological outcome. The retrieved lymph node number cut-off value required for satisfactory D2 lymph node dissection was defined as >25. Cumulative sum analysis was used to examine the learning curves of individual surgeons at target accuracy rates of 85%, 90%, 92.5%, 95%, and 98%. Results: Two junior staff surgeons performed 198 curative-intent total gastrectomies with D2 lymph node dissections during the study period; their success rates exceeded 90%. Operating time decreased with operative experience (Pearson correlation coefficient = -0.515, P < 0.001). The learning period for total gastrectomy with D2 lymph node dissection for these two junior members of staff was calculated as 23-35 cases, presuming a 92.5% success rate. Conclusions: The current study suggests that the surgical learning period for D2 lymph node dissection extends to at least 23 cases or 8 months. In clinical trials containing gastric cancer surgery, the learning curve for qualified surgery from the standpoint of oncological outcome should be considered to minimize bias due to surgeon-associated factors.