Phase II Study of S-1, a Novel Oral Derivative of 5-Fluorouracil, in Advanced Gastric Cancer

<i>Purpose:</i> To assess the efficacy and safety of S-1, a novel oral fluoropyrimidine derivative, we conducted a multicenter late phase II study in patients with advanced gastric cancer. <i>Patients and Methods:</i> Fifty-one patients who had received no previous chemotherapy were enrolled. Fifty patients were eligible for efficacy and safety analyses. The overall response was evaluated for the 43 patients who had metastatic lesions. S-1 was administered orally after breakfast and dinner for 28 days, followed by a 14-day break. The dosages were assigned according to the patients’ body surface area (BSA): BSA <1.25 m<sup>2</sup>, 40 mg; 1.25–1.5 m<sup>2</sup>, 50 mg, and BSA ≥1.5 m<sup>2</sup>, 60 mg, twice daily. <i>Results:</i> The overall response to treatment was evaluated as partial response in 19 of the 43 patients (44%; 95% confidence interval 30–59%). The median survival time in all patients was 207 days with 1- and 2-year survival rates of 36.0 and 14.0%, respectively. Grade 3 adverse reactions included decreased hemoglobin values in 2 patients, leukopenia, neutropenia and diarrhea in 1 patient each. No other grade 4 or unexpected adverse reactions were seen. <i>Conclusions:</i> S-1 is effective against advanced gastric cancer. This oral treatment is suitable for outpatients because of its mild toxicity. Further therapeutic benefits are likely to be obtained by combining S-1 with other chemotherapeutic agents.