A Muti-center, Randomized Phase II Study of Oxaliplatin and S-1 versus Capecitabine and Oxaliplatin in Patients with Metastatic Colorectal Cancer

Background: Capecitabine plus oxaliplatin (XELOX) is considered one of the primary chemotherapy regimens for patients with metastatic colorectal cancer (CRC). Oxaliplatin plus S-1 (OS) has also demonstrated significant efficacy in CRC. We performed this randomized phase II study to evaluate the efficacy and toxicity of XELOX versus OS as first-line chemotherapy in patients with metastatic CRC. Methods: Patients were assigned randomly to receive either OS or XELOX chemotherapy. Oxaliplatin was administered intravenously to all patients at a dose of 130 mg/m(2) on day 1. Patients received either S-1 (40 mg/m(2)) or capecitabine (1,000 mg/m(2)), twice a day for 2 weeks, followed by a 1-week rest. Results: Forty-two patients were assigned to the OS arm and 44 to the XELOX arm. The overall response rate was 33.3% (95% CI, 18.8-47.2) in the OS arm and 40.9% (95% CI, 25.5-54.4) in the XELOX arm (P = 0.230). The disease control rate was significantly higher in the OS arm than the XELOX arm [92.9% (95% CI, 83.7-100) versus 77.3% (95% CI, 64.5-89.4), P = 0.044]. With a median follow up of 17.9 months, the median progression-free survival was 6.1 months in the OS arm and 7.4 months in the XELOX arm, respectively (P = 0. 599). The median survival time was 18.7 months in the OS arm and 20.1 months in the XELOX arm (P = 0.340). The most common grade 3/4 hematologic toxicity was thrombocytopenia in both arms (19.0% for OS and 28.6% for XELOX). Grade 3/4 neutropenia was observed more frequently in the XELOX arm than the OS arm (16.7% vs. 2.4%, P = 0.026). Conclusion: Both OS and XELOX were effective and well tolerated in patients with metastatic CRC. Our results indicate that the combination of oxaliplatin and S-1 is a possible additional therapeutic strategy for such patients.