Low Maruyama Index surgery for gastric cancer

Background: Japanese definitions and treatment guidelines have dominated extent-of-surgery concepts in gastric cancer for over 4 decades, despite the fact that such definitions/guidelines have changed considerably over time, and the fact they have largely failed to improve survival in prospective, randomized clinical trials. Aim: To briefly review lessons from previous surgical trials in gastric cancer, and, more specifically, to review data validating the concept of "'low Maruyama Index surgery" as a data-driven guide to surgical treatment. Methods: Review of results from blinded multivariate analyses of two separate, prospective, randomized clinical trials: a) the Macdonald Trial of adjuvant postoperative chemo-radiation, Intergroup 0116, conducted in North America; and b) the Dutch D1-D2 Trial. Results: Blinded univariate and multivariate analysis of both trials establish "Maruyama Index of Unresected Disease" (MI) < 5 as a strong independent predictor of better disease-free and overall survival in gastric cancer. Moreover, a strong "dose response" effect for MI versus survival is apparent. Conclusions: In contrast to surgery focused on achievement of a particular Japanese-defined D-level, "low Maruyama Index surgery" is associated with increased disease-free and overall survival. Further, the dose-response effect suggests MI can be used to quantify the adequacy of lymphadenectomy for a given patient. Low MI surgery can be prospectively planned by using the Maruyama Computer Program pre-operatively or intraoperatively.