Oxaliplatin, Irinotecan, and Capecitabine in Treating Patients With Advanced or Metastatic Colorectal Cancer That Cannot Be Removed By Surgery

DISEASE CHARACTERISTICS: * Histologically or cytologically confirmed unresectable advanced or metastatic colorectal cancer * Measurable disease (phase II only) * At least 1 unidimensionally measurable lesion ≥ 20 mm by conventional techniques OR ≥ 10 mm by spiral CT scan or MRI * No presence or history of CNS metastases PATIENT CHARACTERISTICS: Age * 18 to 70 Performance status * WHO 0-1 Life expectancy * Not specified Hematopoietic * Absolute neutrophil count ≥ 1,500/mm\^3 * Platelet count ≥ 100,000/mm\^3 Hepatic * Bilirubin ≤ 1.25 times upper limit of normal (ULN) (1.5 times ULN if liver metastases are present) * AST and ALT ≤ 3 times ULN (5 times ULN if liver metastases are present) Renal * Creatinine clearance \> 60 mL/min Cardiovascular * No New York Heart Association class III-IV congestive heart failure * No symptomatic coronary artery disease * No uncontrolled cardiac arrhythmia * No myocardial infarction within the past year * No other clinically significant cardiac disease Immunologic * No active autoimmune disease * No uncontrolled infection * No prior severe reaction to fluoropyrimidine therapy or known hypersensitivity to fluorouracil * No known hypersensitivity to any component of study drugs Other * Not pregnant or nursing * Negative pregnancy test * Patients must use effective contraception during and for 1 year after study participation * No other malignancy within the past 5 years except adequately treated carcinoma in situ of the cervix or localized nonmelanoma skin cancer * No peripheral neuropathy \> grade 1 of any origin (e.g., alcohol or diabetes) * No nausea, vomiting, or malabsorption syndrome that would preclude ingestion or absorption of oral medication * No psychiatric disability that would preclude study compliance * No uncontrolled diabetes * No other serious underlying medical condition that would preclude study participation * No known dihydropyrimidine dehydrogenase deficiency PRIOR CONCURRENT THERAPY: Biologic therapy * No concurrent prophylactic hematopoietic growth factors Chemotherapy * More than 6 months since prior adjuvant fluoropyrimidine chemotherapy * No other prior chemotherapy Endocrine therapy * Not specified Radiotherapy * No concurrent radiotherapy * Concurrent radiotherapy of a single painful lesion allowed Surgery * Not specified Other * More than 30 days since prior clinical trial participation * No other concurrent experimental drugs * No other concurrent anticancer therapy * No concurrent sorivudine or its chemically-related analogues (e.g., lamivudine)