161P - Adjuvant tegafur/gimeracil/oteracil (S-1) versus platinum-based chemotherapies for resectable gastric cancer: Real-world experience and a propensity score matching analysis

Background

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.

Methods

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.

Results

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.

Conclusions

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.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.