Combination chemotherapy of S-1 and low-dose cisplatin for advanced gastric cancer

A previous phase II study showed that S-1 (TS-1) was effective for advanced gastric cancers and had mild toxicity. The present study aimed to evaluate the efficacy and feasibility of this novel anticancer drug combined with low-dose cisplatin (CDDP).

Fifteen patients with unresectable and recurrent gastric cancer were enrolled. S-1 was administered orally twice daily after meals, at a standard dose of 80 mg/m2 per day according to the late phase II trial protocol. One course consisted of 28 days' consecutive administration followed by 14 days' rest. Five or 10 mg CDDP was infused three times each week (days 1, 3, 5) during S-1 administration on hospitalization, and once each week (day 1) at the outpatient clinic. Patients' backgrounds, response rates, response durations, and time to progression were investigated.

None of the 15 patients had a complete response and 8 had a partial response. Therefore, the overall response rate was 53% (8/15). For site efficacy, the response rate was 50% (5/10) for the primary lesion, 50% (3/6) for liver metastasis, and 39% (5/13) for lymph node metastasis. The median response duration of the 8 responders was 4 months, and the time to progression was 3.3 months. Adverse reactions appeared in 60% (9/15). The incidence of adverse reactions of grades 3 and 4 was 13% (2/15) and 0%, respectively. As for hematological toxicity, grade 3 leukopenia was observed in 2 patients (2/15), but decreased hemoglobin level and thrombocytopenia did not appear. Although gastrointestinal adverse reactions appeared in 40% (6/15), all reactions were grades 1 and 2. Because of the mild toxicity, most patients were treated at the outpatient clinic.

Combination chemotherapy of S-1 and low-dose CDDP is expected to be a useful chemotherapy for advanced gastric cancer.