Influence of Hospital and Surgeon Volumes on Clinical Outcomes After Standard Surgery for Advanced Gastric Cancer: Supplementary Analysis of the Multicenter Randomized Phase III Trial JCOG1001.

Aim: Higher volumes of surgical procedures have been associated with better patient outcomes. However, few large-scale studies have evaluated interinstitutional variation to verify the generalization and standardization of gastric cancer surgery. Methods: A randomized phase III trial (JCOG1001) was conducted to compare standard and experimental surgeries for advanced gastric cancer. Of the 1204 patients with cT3-4b gastric adenocarcinoma enrolled in JCOG1001 between 2010 and 2015, this study only included hospitals that enrolled at least three patients and patients in the standard surgery arm in this analysis. Mixed-effects models were used to examine the short- and long-term outcome data for 595 patients from 47 institutes after adjusting for clinical backgrounds. Spearman's correlation coefficients were calculated for associations between the estimated outcomes and hospital or surgeon volumes. Results: A degree of variation in the 5-year overall survival (OS) for standard gastric surgery in each hospital after adjusting for background was observed in the JCOG1001 patients (median, 81%; range, 61%-89%). For standard gastric surgery, a higher surgeon volume was significantly but weakly correlated with a higher proportion of patients with postoperative complications ( Conclusions: Although there was some degree of interinstitutional variation in short- and long-term outcomes after standard gastric surgery, we found no correlation between long-term outcomes and hospital or surgeon volumes in JCOG1001.