Oxaliplatin and S-1 (OS) Versus Oxaliplatin and Capecitabine (XELOX) for Advanced Colorectal Cancer

Inclusion Criteria: * Histologically confirmed colorectal adenocarcinoma, initially diagnosed or recurred * Unresectable, locally advanced or metastatic * At least one uni-dimensional measurable lesion by RECIST criteria * Age 18 to 75 years old * Estimated life expectancy ≥3 months * ECOG performance status ≤2 * Adequate bone marrow function (WBCs ≥ 4,000/µL or absolute neutrophil count ≥ 1,500/µL, platelets ≥ 100,000/µL) * Adequate kidney function (creatinine \< 1.5 mg/dL) * Adequate liver function (bilirubin \< 2.0 mg/dL, transaminase levels \<2.5 times the upper normal limit) * Written informed consent Exclusion Criteria: * Other tumor type than adenocarcinoma * Previous history of chemotherapy (exception : neoadjuvant or adjuvant chemotherapy without oxaliplatin) * Presence of CNS metastasis, psychosis, or seizure * Obvious bowel obstruction * Evidence of serious gastrointestinal bleeding * Past or concurrent history of neoplasm other than colorectal adenocarcinoma, except for curatively treated non-melanoma skin cancer or in situ carcinoma of the cervix uteri * Pregnant or lactating women, women of childbearing potential not employing adequate contraception * Other serious illness or medical conditions