RATIONALE: Drugs used in chemotherapy use different ways to stop tumor cells from dividing so they stop growing or die. Combining more than one drug may kill more tumor cells.

PURPOSE: Phase II trial to study the effectiveness of combination chemotherapy in treating patients who have metastatic colorectal cancer that has not responded to previous chemotherapy.

OBJECTIVES: I. Determine the efficacy of oxaliplatin, leucovorin calcium, and fluorouracil followed by irinotecan, leucovorin calcium, and fluorouracil in terms of progression free survival in patients with metastatic colorectal cancer. II. Evaluate these treatment regimens in terms of overall survival, response rate, toxicity, and quality of life in this patient population.

OUTLINE: This is a multicenter study. Patients receive 4 courses of oxaliplatin IV and leucovorin calcium IV over 2 hours on day 1 followed by fluorouracil IV continuously over 46 hours. Following the initial 4 courses of therapy, patients receive 4 courses of irinotecan IV over 30-90 minutes and leucovorin calcium IV over 2 hours on day 1 followed by fluorouracil IV continuously over 46 hours. Courses repeat every 2 weeks in the absence of disease progression or unacceptable toxicity. Quality of life is assessed every 8 weeks. Patients are followed every 3 months until death.

PROJECTED ACCRUAL: A total of 14-39 patients will be accrued for this study over 12 months.

DISEASE CHARACTERISTICS: Histologically confirmed metastatic adenocarcinoma of the colon or rectum Measurable or evaluable lesion or residual disease (e.g., ascites, bone metastases) Failure after first line therapy Fluorouracil and leucovorin calcium OR Raltitrexed No oxaliplatin or irinotecan Relapse within 6 months of adjuvant therapy Relapse within 6 months of hepatic artery infusion chemotherapy for resected hepatic metastasis No symptomatic brain metastasis

PATIENT CHARACTERISTICS: Age: 18 to 80 Performance status: WHO 0-2 Life expectancy: At least 3 months Hematopoietic: Absolute neutrophil count at least 1,500/mm3 Hepatic: AST and ALT no greater than 3 times upper limit of normal (ULN) Alkaline phosphatase no greater than 5 times ULN Renal: Not specified Other: No bowel obstruction No other significant, uncontrolled underlying medical or psychiatric condition No serious active infection Neurologically stable No other prior malignancy except nonmelanomatous skin cancer or carcinoma in situ of the cervix No psychological, social, familial, or geographical condition that would preclude study Not pregnant or nursing Fertile patients must use effective contraception

PRIOR CONCURRENT THERAPY: Biologic therapy: Not specified Chemotherapy: See Disease Characteristics Endocrine therapy: Not specified Radiotherapy: At least 2 weeks since prior radiotherapy Surgery: At least 2 weeks since prior surgery Other: No other concurrent experimental drugs