Comparison of surgical outcomes in laparoscopic gastrectomy for advanced gastric cancer between Japanese and Italian cohorts: an international, propensity score-matched investigation (the Shinkansen Study)

Background Marked differences in advanced gastric cancer (AGC) surgical outcomes have historically been documented between Eastern and Western centers. This study compared laparoscopic gastrectomy (LG) surgical outcomes for AGC between Japanese and Italian institutions. Methods This international, retrospective cohort study included patients undergoing LG for AGC at 17 Italian (within the Italian Research Group for Gastric Cancer) and 5 Japanese institutions (2015-2022). Propensity score matching (PSM) was used to balance baseline characteristics. The primary endpoint was 90-day severe morbidity (Clavien-Dindo >= III). Secondary endpoints were 90-day mortality, R0 resection rates, and lymph node (LN) yield. Multivariable regression identified predictors of severe morbidity. Results From 1,617 patients, PSM selected 566 cases (283 per group). The Italian group (IG) showed a trend toward higher 90-day severe morbidity (14.8% vs. 9.2%, p = 0.052) and 90-day mortality (1.8% vs. 0.4%, p = 0.218) compared to the Japanese group (JG), though differences were not statistically significant. R0 resection rates were similar (96.1% vs. 98.6%, p = 0.115). Median harvested LNs were lower in the IG (34 vs. 43, p < 0.001). Multivariable analysis identified male sex and total gastrectomy, but not country of surgery, as independent predictors of 90-day severe morbidity. Conclusions In propensity-matched cohorts, LG for AGC showed a clinical trend favoring the JG regarding severe morbidity, without reaching statistical significance. Country of surgery was not an independent predictor of severe complications. While some results are converging, suggesting an acceptable quality of care in Western institutions, the historical surgical gap between these specific Eastern and Western settings has not been completely bridged and better surgical outcomes in Japan persist.