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