Upfront Surgery Versus NeoAdjuvant Chemotherapy Followed by Surgery for Resectable Advanced Gastric Cancer (SNAC Study): An Observational Retrospective Multicenter Study With Matched Treatment Comparison

Based on the concerns about the actual low strength of evidence of the efficacy of NAC on survival of proper gastric cancer treated with adequate D2 gastrectomy as compared to the results of optimal upfront surgery (S), and considering the actual difficulties of additional RCTs, the aim of this study is to assess the non-inferiority of upfront surgery alone with optimal D2 dissection compared to NAC regimens followed by surgery. Methods: This is a nationwide Multicenter observational retrospective study with matched comparison of two therapeutic strategies (NAC vs S). We will include patients with cT>2, every cN M0, or with every T and N+ M0, histologically proven adenocarcinoma of the stomach, submitted either to pre- or peri-operative treatment and D2 gastrectomy or to upfront D2 gastrectomy, between January 2012 and December 2019, followed by adjuvant treatment when recommended.

All patients matching the inclusion/exclusion criteria will be registered into the study and classified into one of the two arms: a, patients who underwent pre- or perioperative treatment and D2 gastrectomy (NAC) or b, patients submitted to upfront D2 gastrectomy (S). Given the results reported in the "FLOT" trial, a 3-years OS of 55% in the control arm (NAC) was assumed. Three-year OS in the experimental arm (S) was assumed to be 47.4% under the null hypothesis of inferiority and 55% under the alternative hypothesis of non-inferiority. A sample size of 684 patients (342 in each arm) achieves 80% power to detect a non-inferiority margin Hazard Ratio of 1.25