Postoperative adjuvant chemotherapy has changed the clinical paradigm in resectable gastric cancer. S-1 is an orally available chemotherapeutic with promising efficacy in Asia. However, the real-world experience of adjuvant S-1 in patients with resectable gastric cancer is seldom reported. A comparison with other platinum-based chemotherapies also warrants further investigation.
We retrospectively evaluated patients with resectable stage I to III gastric cancer who received S-1 (S-1, n=52), platinum-based chemotherapies (Platinum, n=85) and operation alone (OP, n=128) from Jan 2013 to Oct 2018. Recurrence-free (RFS) and overall survivals (OS) were compared with a propensity score matching analysis. Adverse effects, dosage and predictive factors for S-1 were also described.
Group OP and S-1 had more patients with early stages of the disease as compared with Others. In a median follow-up of 39.4 months, Group S-1 had a trend of longer RFS and OS as compared with Platinum but it did not reach statistical significance (5-year RFS/OS rates: S-1 vs. Platinum, 49.5/58.3% vs. 40.2/50.6%, HR=0.85/0.70, p=0.575/0.330). Group S-1 with N3 disease had significantly longer RFS (S-1 vs. Platinum, undefined vs. 17.3 months, HR=0.33, p=0.046) but the OS difference was insignificant. S-1 was well-tolerated while platinum-doublets were associated with more severe adverse effects. The relative dose intensity of S-1 was 71.8%. In the subgroup analyses, patients with N3 disease, diffuse type tumors and Helicobacter pylori infection were potentially favorable in RFS when treated with adjuvant S-1. Early disease stages, N0 disease and low CEA were independent predictors for the selection of S-1.
Patients with resectable gastric cancer who received adjuvant S-1 had a comparable survival but better tolerability as compared with platinum-based regimens. Patients with diffuse type tumor, Helicobacter pylori infection and N3 disease derived additional benefits from S-1. The real-world experience revealed that S-1 was relatively under-dosed and selected according to disease stage, lymph node involvement and CEA level.
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All authors have declared no conflicts of interest.