DISEASE CHARACTERISTICS: Histologically confirmed colorectal carcinoma Inoperable advanced recurrent or metastatic disease Measurable disease outside previously irradiated area No CNS metastases

PATIENT CHARACTERISTICS: Age: 18 to 74 Performance status: WHO 0-1 Life expectancy: More than 12 weeks Hematopoietic: WBC greater than 4,000/mm3 Platelet count greater than 100,000/mm3 Hepatic: Bilirubin less than 1.25 times upper limit of normal (ULN) SGOT less than 1.25 times ULN Albumin greater than 3.5 g/dL Renal: Creatinine clearance greater than 70 mL/min Cardiovascular: No history of congestive heart failure, myocardial infarction within the past 6 months, active ischemic heart disease, or uncontrolled hypertension Other: No weight loss more than 10% in the last 2 months No other prior malignancy except curatively treated carcinoma in situ of the cervix or non-melanoma skin cancer No history of alcohol abuse No uncontrolled medical or psychiatric disease Not pregnant or nursing Fertile patients must use effective contraception

PRIOR CONCURRENT THERAPY: Biologic therapy: No concurrent filgrastim (G-CSF) Chemotherapy: No prior chemotherapy for advanced disease Recovered from prior adjuvant therapy No other concurrent chemotherapy Endocrine therapy: Not specified Radiotherapy: See Disease Characteristics No prior radiotherapy for advanced disease Surgery: See Disease Characteristics Other: No other concurrent therapy