Inclusion Criteria

DISEASE CHARACTERISTICS:

- Histologically confirmed locally advanced, locally recurrent, or metastatic
colorectal adenocarcinoma

- At least 1 measurable lesion

- At least 10 mm by spiral CT scan

- At least 20 mm by conventional techniques

- Bone metastases, ascites, or pleural effusions are not considered measurable
disease

- No evidence of CNS metastases

PATIENT CHARACTERISTICS:

Age:

- 18 and over

Performance status:

- Karnofsky 80-100%

Life expectancy:

- Not specified

Hematopoietic:

- Neutrophil count at least 1,500/mm^3

- Platelet count at least 100,000/mm^3

Hepatic:

- Bilirubin no greater than 1.25 times upper limit of normal (ULN)

- ALT and AST no greater than 2.5 times ULN (5 times ULN if liver metastases present)

- Alkaline phosphatase no greater than 2.5 times ULN (5 times ULN if liver metastases
present or 10 times ULN if bone metastases present)

- No known Gilbert's disease

Renal:

- Creatinine no greater than 1.5 times ULN

- Creatinine clearance at least 50 mL/min

Cardiovascular:

- No clinically significant cardiac disease

- No congestive heart failure

- No symptomatic coronary artery disease

- No cardiac arrhythmias uncontrolled with medication

- No myocardial infarction within the past 12 months

Gastrointestinal:

- Able to swallow tablets

- No lack of physical integrity of the upper gastrointestinal tract

- No malabsorption syndrome

Other:

- No prior unanticipated severe reaction to fluoropyrimidine therapy

- No hypersensitivity to fluorouracil

- No history of uncontrolled seizures or CNS disorders

- No psychological illness or condition that would preclude study entry

- No other malignancy within the past 5 years except curatively treated basal cell skin
cancer or carcinoma in situ of the cervix

- No serious infection

- Not pregnant or nursing

- Negative pregnancy test

- Fertile patients must use effective contraception

PRIOR CONCURRENT THERAPY:

Biologic therapy:

- At least 12 months since prior neoadjuvant or adjuvant, active or passive
immunotherapy

- No concurrent active or passive immunotherapy (e.g., 17-1A antibody) for colon cancer

- No concurrent prophylactic hematopoietic growth factors

Chemotherapy:

- At least 12 months since prior neoadjuvant or adjuvant cytotoxic chemotherapy

- No prior chemotherapy for metastatic colorectal cancer

- No prior irinotecan or capecitabine

- No other concurrent cytotoxic agents

Endocrine therapy:

- Not specified

Radiotherapy:

- At least 4 weeks since prior radiotherapy

- No prior radiotherapy to measurable lesion (newly arising lesions in a previously
irradiated area allowed)

- No concurrent radiotherapy

Surgery:

- At least 4 weeks since prior major surgery and recovered

- No prior organ allograft

Other:

- At least 4 weeks since prior participation in an investigational drug study

- No other concurrent investigational drugs