Low Maruyama Index Surgery for Gastric Cancer: Blinded Reanalysis of the Dutch D1-D2 Trial

A quantitative estimate of residual nodal disease after gastric cancer surgery, the Maruyama index of unresected disease (MI), proved to be a strong independent predictor of survival in a large U.S. adjuvant chemoradiation study in which surgical undertreatment was frequent. Data from the Dutch D1-D2 Lymphadenectomy Trial permit an opportunity to assess the prognostic value of this variable in a cohort with lower-stage disease treated with minimum D-1 lymphadenectomy and no adjuvant chemoradiation. Blinded to survival, and excluding those cases with missing information, the MI was calculated for 648 of the original 711 patients treated with curative intent. Survival was assessed by log-rank and multivariate Cox regression analysis. All patients have been followed for a minimum of 11 years. Overall Dutch trial findings were not affected by the absence of 63 cases with incomplete data. As expected, the median MI was 26, much lower than in the previous U.S. study. In contrast to the D level, MI < 5 proved to be a strong predictor of survival by both univariate and multivariate analysis. The MI was an independent predictor of both overall survival [P = 0.016; hazard ratio (HR) = 1.45; 95% confidence interval (CI) 1.07–1.95] and relapse risk (P = 0.010; HR = 1.72; 95% CI 1.14–2.60). A strong dose-response reaction with respect to the MI and survival was also observed. We conclude that in this trial low-MI surgery is associated with enhanced survival, whereas outside of certain subgroups routine D2 lymphadenectomy is not. This observation suggests that surgeons might have more of an impact on patient survival by achieving a low-MI operation than a particular D level. A compelling dose-response effect reveals that the MI is a quantitative yardstick for assessing the adequacy of lymphadenectomy in gastric cancer.