S-1 in the treatment of advanced and recurrent gastric cancer: Current state and future prospects

Background. S-1 (TS-1®) is a novel oral anticancer drug. Because of the excellent results of phase II studies, we continued to prescribe S-1 for advanced or recurrent gastric cancer after we participated in the phase I and II studies. Methods. Twenty-nine patients with advanced or recurrent gastric cancer were treated with S-1. Clinicopathological features, survival, and adverse reactions were analyzed. Results. One course of treatment consisted of 40, 50, or 60 mg/body twice a day for 28 days followed by withdrawal for 2 weeks. The mean number of treatments was 3.6 courses (range, 1-12 courses). The response rate was 37.9% (11 partial responses [PRs] in 29 patients). Although the response rate of patients who did not receive prior chemotherapy was 47.6% (10 PRs in 21 patients), that of patients with prior chemotherapy was 12.5% (1 PR in 8 patients). The median survival time was 14.1 months, and that of patients who responded to treatment was 22.1 months, which was significantly longer than that of nonresponder patients. One-year and 2-year survivals in the 29 patients were 50.2% and 24.3%, respectively. Adverse reactions were noted in 17 of 29 patients, and the most frequent one was leukocytopenia. Only 2 patients experienced grade 3 leukocytopenia and neutrocytopenia. Conclusion. Because of the high response rate and low incidence of severe adverse reactions, S-1 is a first-line chemotherapy that can be used for outpatients, especially for patients without prior chemotherapy. As the response rate for patients with prior chemotherapy was low, combined therapy with S-1 is worth evaluating for these patients.