Inclusion Criteria:

- Histologically confirmed unresectable or metastatic colorectal cancer, not amenable
to surgery or radiation treatment for curative intent

- At least one unidimensional measurable lesion

- ECOG performance status 0-2.

- No prior chemotherapy in metastatic settings, but adjuvant or neo-adjuvant treatment
for non-metastatic (M0) disease is allowed if completed at least 6 months prior to
initiation of study treatment

- Adequate major organ functions

- Give written informed consent

Exclusion Criteria:

- Prior systemic chemotherapy for metastatic disease

- Prior treatment with oxaliplatin or irinotecan

- Prior radiotherapy is permitted if it was not administered to target lesions selected
for this study and provided it has been completed at least 4 weeks before
registration

- Prior surgical treatment of stage IV disease is permitted

- CNS metastases

- Prior history of peripheral neuropathy ≥ NCI CTC grade 1

- Uncontrolled or severe cardiovascular disease

- Serious concurrent infection or nonmalignant illness

- Other malignancy within the past 3 years except cured non-melanomatous skin cancer or
carcinoma in situ of the cervix

- Organ allografts requiring immunosuppressive therapy

- Psychiatric disorder or uncontrolled seizure that would preclude compliance

- Pregnant, nursing women or patients with reproductive potential without contraception

- Patients receiving a concomitant treatment with drugs interacting with S-1 such as
flucytosine, phenytoin, or warfarin et al.

- Prior unanticipated severe reaction to fluoropyrimidine therapy, or known
dihydropyrimidine dehydrogenase (DPD) deficiency

- Known hypersensitivity to platinum compounds or any of the components of the study
medications

- Major surgery within 3 weeks prior to study treatment starts, or lack of complete
recovery from the effects of major surgery

- Received any investigational drug or agent/procedure, i.e. participation in another
trial within 4 weeks before beginning treatment with study drug