DISEASE CHARACTERISTICS:

• Histologically confirmed colorectal adenocarcinoma

  • Metastatic, unresectable disease

• Meets 1 of the following criteria:

  • At least 1 unidimensionally measurable metastatic lesion at least 10 mm by spiral scan OR 20 mm by conventional scan
  • Evaluable disease
  • Evidence of disease (e.g., ascites or bone metastases) by imaging techniques

• Progressive disease as defined by 1 of the following criteria:

  • Progressive disease while receiving first-line chemotherapy
  • Recurrent disease within 6 months after completing adjuvant chemotherapy
• No symptomatic brain metastases

PATIENT CHARACTERISTICS:

Age

• 18 to 80

Performance status

• WHO 0-2

Life expectancy

• At least 3 months

Hematopoietic

• Absolute neutrophil count ≥ 1,500/mm^3
• Platelet count ≥ 100,000/mm^3

Hepatic

• Bilirubin < 1.5 times upper limit of normal (ULN)
• Alkaline phosphatase < 3 times ULN

Renal

• Not specified

Cardiovascular

• No uncontrolled angina
• No myocardial infarction within the past 6 months

Gastrointestinal

• No chronic diarrhea grade 2 or greater
• No unresolved fully or partially obstructed intestine

Other

• Not pregnant or nursing
• Fertile patients must use effective contraception
• No other underlying disease or medical condition that would preclude study participation
• No other prior malignancy except curatively treated basal cell cancer or carcinoma in situ of the cervix
• No psychological, social, familial, or geographical condition that would preclude study follow-up

PRIOR CONCURRENT THERAPY:

Biologic therapy

• Not specified

Chemotherapy

• See Disease Characteristics
• No prior irinotecan

Endocrine therapy

• Not specified

Radiotherapy

• At least 3 weeks since prior radiotherapy

Surgery

• At least 3 weeks since prior surgery

Other

• No other concurrent clinical trial participation