Multicenter phase II Study of gemcitabine and S-1 combination therapy (GS Therapy) in patients with metastatic pancreatic cancer

Objective: The aim of this multicenter Phase II study was to assess the efficacy and toxicity of gemcitabine and S-1 combination therapy for metastatic pancreatic cancer. Methods: Chemotherapy-naive patients with histologically or cytologically proven metastatic pancreatic adenocarcinoma were eligible for this study. Gemcitabine was administered at a dose of 1000 mg/m 2 over 30 min on days 1 and 8, and oral S-1 at a dose of 40 mg/m 2 twice daily from days 1 to 14, repeated every 3 weeks. Results: A total of 55 patients were included and the efficacy and toxicity were analyzed in 54 patients who received at least one dose of gemcitabine and S-1 combination therapy. Although no complete response was seen, a partial response was achieved in 24 patients, resulting in an overall response rate of 44.4% (95% confidence interval: 30.9-58.6%). The median progression-free survival was 5.9 months (95% confidence interval: 4.1-6.9 months) and the median overall survival was 10.1 months (95% confidence interval: 8.5-10.8 months) with a 1-year survival rate of 33.0%. The major Grade 3-4 toxicities were neutro- penia (80%), leucopenia (59%), thrombocytopenia (22%), anorexia (17%) and rash (7%). Hematological toxicity was mostly transient and there was only one episode of febrile neutro- penia Grade 3. Conclusions: Gemcitabine and S-1 combination therapy produced a high response rate with good survival in patients with metastatic pancreatic cancer. A randomized Phase III study to confirm the efficacy of gemcitabine and S-1 combination therapy is ongoing.