Inclusion Criteria

DISEASE CHARACTERISTICS:

- Histologically confirmed adenocarcinoma of the colon or rectum

- Metastatic, locally advanced, or recurrent disease

- Patients must have at least 2 generations (parents and grandparents) who belong to
one of the following racial groups:

- Asian or Pacific Islander (e.g., China, Japan, Korea, the Philippine Islands, or
Samoa)

- Black (originating from the black racial groups of Africa)

- Hispanic (originating from Mexico, Puerto Rico, Cuba, Central or South America,
or other Spanish culture)

- White (originating from the peoples of Europe, North Africa, or the Middle East)

- No patients with parents or grandparents of mixed race or race other than that of the
patient

PATIENT CHARACTERISTICS:

Age:

- Not specified

Performance status:

- CTC 0-2

Life expectancy:

- Not specified

Hematopoietic:

- Granulocyte count at least 1,500/mm3

- Platelet count at least 100,000/mm3

Hepatic:

- Bilirubin no greater than 1.5 mg/dL

- AST no greater than 3 times upper limit of normal

Renal:

- Creatinine no greater than 1.5 mg/dL

Other:

- Not pregnant or nursing

- Fertile patients must use effective contraception

PRIOR CONCURRENT THERAPY:

Biologic therapy:

- Not specified

Chemotherapy:

- Prior adjuvant fluorouracil allowed if relapse occurred at least 6 months after
completion of fluorouracil

- At least 4 weeks since prior chemotherapy (6 weeks for nitrosoureas or mitomycin)

- No prior irinotecan

- No other concurrent chemotherapy

Endocrine therapy:

- No concurrent hormones except steroids for adrenal failure, hormones for nondisease
related conditions (e.g., insulin for diabetes), or intermittent dexamethasone as an
antiemetic

- No concurrent prednisone

Radiotherapy:

- At least 4 weeks since prior radiotherapy (except to bone or soft tissue involving
less than 25% of bone marrow)

- No concurrent radiotherapy

Surgery:

- At least 4 weeks since prior major surgery

Other:

- No concurrent phenobarbital, valproate, or cyclosporine

- None of the following concurrently during first course of therapy:

- Macrolide antibiotics (e.g., azithromycin, erythromycin, clarithromycin,
troleandomycin, dapsone)

- Azole antibiotics (e.g., fuconazole, miconazole, itraconazole, ketoconazole)

- Triazobenzodiazepines (e.g., alprazolam, midazolam, triazolam)

- Antidepressants (e.g., fluoxetine, setraline hydrochloride, fluoxamine,
nefazodone hydrochloride)

- Quinolone antimicrobials (e.g., ciprofloxacin, ofloxacin)

- Imidazole antibiotics (e.g., clotrimazole)

- Anti-ulcer medications (e.g., omeprazole, lansoprazole)

- Ethinyl estradiol

- Diltiazem

- Cimetidine hydrochloride

- Cisapride

- Terfenadine

- Rifampin

- Glucocorticoids

- Antiepileptics

- Grapefruit juice