S-1 versus Doublet Regimens as Adjuvant Chemotherapy in Patients with Advanced Gastric Cancer after Radical Surgery with D2 Dissection-A Propensity Score Matching Analysis

Background: Fluoropyrimidine- and platinum-based doublet regimen is the standard treatment of adjuvant chemotherapy (AC) for gastric cancer (GC). Our study aims to compare S1 with doublet regimens as AC in patients with advanced GC after radical surgery with D2 dissection. Methods: Patients who were diagnosed with GC and underwent a curative surgery with D2 dissection followed by AC were enrolled into our study. A propensity score matching analysis was performed to reduce the selection bias. Kaplan-Meier curves were estimated for recurrence-free survival (RFS) and overall survival (OS). Cox regression models were conducted for survival. Results: After propensity sore matching, 64 patients with S1 and 64 patients with doublet regimens were identified. The median RFS (p= 0.355) and OS (p= 0.309) were both insignificant between S1 and ST. Cox regression analysis demonstrated that pathologic stage and lymph node ratio (LNR) were independently correlated with survival. Patients were then stratified into low risk and high risk groups. The median RFS (p< 0.001) and OS (p< 0.001) had significant differences between low risk and high risk. In the high-risk group, doublet regimens were strongly associated with survival (p= 0.020) as compared with S1. While in the low-risk group, doublet regimen and S1 did not have statistically different survival benefits. Conclusions: Our study demonstrated that doublet regimens are superior to S1 in high-risk groups, and that survival outcomes are similar between doublet regimens and S1 in low-risk groups. Our prognostic model might have clinical implications for AC.