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.