Combination Chemotherapy in Treating Patients With Colorectal Cancer

DISEASE CHARACTERISTICS: Histologically confirmed colorectal cancer Unresectable metastatic or locoregional disease At least 1 measurable lesion outside a previously irradiated area or an area treated with physical devices (e.g., cryotherapy, laser, or thermoablation) No prior enrollment in EORTC-05963 No symptomatic brain metastases PATIENT CHARACTERISTICS: Age: Over 18 Performance status: WHO 0-2 Life expectancy: Not specified Hematopoietic: Neutrophil count greater than 2,000/mm^3 Platelet count at least 90,000/mm^3 Hepatic: Bilirubin no greater than 2 times upper limit of normal (ULN) Renal: Creatinine no greater than 1.5 times ULN No uncontrolled hypercalcemia Cardiovascular: No overt cardiac disease Pulmonary: No severe respiratory illness Other: Not pregnant or nursing Negative pregnancy test Fertile patients must use effective contraception Male patients must use effective barrier contraception during and for up to 6 months after study No baseline diarrhea greater than grade I (must have less than 4 stools per 24 hours) No prior grade III or IV toxicity related to irinotecan No sensory or motor neuropathy with functional impairment No prior hypersensitivity to any study drug No other primary tumor except basal cell skin cancer or carcinoma in situ of the cervix No uncontrolled infectious or chronic disease No psychological, familial, sociological, or geographical condition that would preclude study PRIOR CONCURRENT THERAPY: Biologic therapy: No concurrent prophylactic growth factor therapy Chemotherapy: At least 1 month since prior chemotherapy No prior irinotecan, fluorouracil, leucovorin calcium, and oxaliplatin as combination therapy Other prior therapy containing irinotecan and/or oxaliplatin allowed No more than 1 prior chemotherapy regimen for metastatic or locoregional disease Adjuvant chemotherapy considered first-line therapy if tumor relapsed within 6 months of completion of therapy Endocrine therapy: No concurrent corticosteroids except for emergencies Radiotherapy: See Disease Characteristics Palliative radiotherapy for bone lesion allowed except for disease progression Surgery: See Disease Characteristics