Study of S-1 and Oxaliplatin (SOX) Versus Capecitabine and Oxaliplatin (COX) in Patients With Advanced Colorectal Cancer

Inclusion Criteria:

* Histologically documented colorectal adenocarcinoma
* Age over 18 years old
* Performance status (ECOG scale): 0-2
* Measurable or evaluable disease
* Patients can take food and drugs orally
* Adequate organ functions
* Life expectancy ≥ 3 months
* Patients should sign a written informed consent before study entry

Exclusion Criteria:

* Tumor type other than adenocarcinoma
* Second primary malignancy
* Prior systemic therapy (for instance, cytotoxic chemotherapy or active/passive immunotherapy) for advanced or metastatic colorectal cancer
* Adjuvant or neo-adjuvant treatment for non-metastatic (M0) disease has been completed within 6 months prior to initiation of study treatment.
* Prior radiotherapy was administered to target lesions selected for this study, or radiotherapy to the non-target lesions has been completed within 4 weeks before randomization.
* Presence of CNS metastasis
* Obvious peritoneal seeding or bowel obstruction disturbing oral intake
* Symptomatic peripheral neuropathy
* Major surgery within 4 weeks prior to study treatment start, or lack of complete recovery from the effects of major surgery. The patient received curative operation or RFA for metastatic disease.
* Serious illness or medical conditions
* Receiving a concomitant treatment with drugs interacting with S-1, capecitabine or oxaliplatin, as follows;flucytosine, a fluorinated pyrimidine antifungal agent phenytoin warfarin etc.
* Received any investigational drug or agent/procedure, i.e. participation in another trial within 4 weeks before beginning treatment with study drug.
* Pregnant or lactating woman
* Women of child bearing potential not using a contraceptive method
* Sexually active fertile men not using effective birth control during medication of study drug and up to 6 months after completion of study drug if their partners are women of child-bearing potential
* Any patients judged by the investigator to be unfit to participate in the study