DISEASE CHARACTERISTICS:

• Histologically confirmed colorectal carcinoma

  • Metastatic disease
• Not amenable to surgery
• Unidimensionally measurable disease
• No bone metastases
• No brain metastases

PATIENT CHARACTERISTICS:

Age

• 18 to 75

Performance status

• WHO 0-2

Life expectancy

• At least 12 weeks

Hematopoietic

• Neutrophil count at least 2,000/mm^3
• Platelet count at least 100,000/mm^3
• Hemoglobin at least 10 g/dL

Hepatic

• Bilirubin no greater than 1.25 times upper limit of normal (ULN) (1.5 times ULN if hepatic metastases are present)
• SGPT and SGOT no greater than 3 times ULN (5 times ULN if hepatic metastases are present)

Renal

• Creatinine no greater than 1.25 times ULN

Cardiac

• No concurrent cardiac abnormalities that would preclude study therapy

Pulmonary

• No concurrent pulmonary abnormalities that would preclude study therapy

Other

• Not pregnant or nursing
• Fertile patients must use effective contraception
• No chronic enteropathy
• No other prior cancer within the past 5 years except carcinoma in situ of the cervix or curatively treated basal cell skin cancer
• No concurrent severe uncontrolled infection
• No obstruction or partial obstruction that would interfere with study therapy
• No psychological, social, familial, or geographical situation that would preclude study participation

PRIOR CONCURRENT THERAPY:

Biologic therapy

• No concurrent anticancer biological response modifiers

Chemotherapy

• No prior chemotherapy (except adjuvant chemotherapy completed more than 6 months ago)
• No prior irinotecan
• No prior oxaliplatin
• No other concurrent chemotherapy

Endocrine therapy

• No concurrent anticancer hormonal therapy

Radiotherapy

• At least 4 weeks since prior pelvic radiotherapy
• No prior abdominopelvic radiotherapy

Surgery

• At least 4 weeks since prior surgery
• No prior extensive intestinal resection (i.e., more than 1 prior hemicolectomy or extensive resection of the small intestines)

Other

• No other concurrent experimental medication
• No other concurrent anticancer therapy