Phase I/II Study of S-1 Plus Cisplatin Alternating with S-1 Plus Docetaxel in Patients with Advanced Gastric Cancer

Objectives: To investigate the usefulness of S-1 plus cisplatin alternating with S-1 plus docetaxel as first-line treatment in patients with advanced gastric cancer, we conducted a phase I/II study to determine the maximum tolerated dose and recommended dose, and evaluate efficacy and toxicity. Materials and Methods: Patients with histologically confirmed unresectable and recurrent gastric cancer were enrolled in this study. Cisplatin was administered on day 1 and the dose escalated by 10 mg/m 2 from a starting dose of 40 mg/m 2 in the phase I part. S-1 was given orally at 80 mg/m 2 on days 1 to 14 and docetaxel at 40 mg/m 2 on day 22 in combination with S-1 80 mg/m 2 on days 22 to 35. The treatment was repeated every 6 weeks. The primary endpoint of the phase II analysis was the response rate. Results: Nine patients entered the phase I and 24 the phase II part. Because 50% of patients (3/6) developed dose-limiting toxicities in the phase I part, the maximum tolerated dose of cisplatin was presumed to be 50 mg/m 2. Therefore, the estimated recommended dose of cisplatin was 40 mg/m 2; 27 patients received that dose. The response rate was 59.3% (95% confidence interval, 40.8-77.8) and the median follow-up 26.2 months. The median progression-free survival was 7.9 months and the median overall survival 18.6 months. The most common grade 3/4 toxicities were neutropenia (59.3%), leucopenia (37.0%), and anemia (29.6%). These toxicities were tolerable and manageable. Conclusion: This alternating treatment seems to have promising activity with tolerable toxicities in the first-line treatment of patients with advanced gastric cancer.