DISEASE CHARACTERISTICS:

Unresectable primary colorectal adenocarcinoma that is metastatic or recurrent.

Objectively measurable disease required.

No cerebral metastases.

PRIOR/CONCURRENT THERAPY:

Biologic Therapy:

No history of intolerance to interferon alfa (IFN-A).

At least 4 weeks since immunotherapy and recovered.

Chemotherapy: No prior chemotherapy for metastatic or recurrent disease. At least 6 months since adjuvant chemotherapy with fluorouracil (5-FU) in combination with levamisole, leucovorin (CF), or IFN-A Interval waived for 5-FU (with or without CF) as a radiosensitizer only . No dose-limiting toxicity with prior 5-FU.

Endocrine Therapy: Not specified

Radiotherapy: At least 2 weeks since palliative radiotherapy and recovered. Prior definitive pelvic or whole or upper abdominal radiotherapy allowed in the absence of current radiation enteritis.

Surgery: Prior surgery allowed with adequate healing/recovery

Patient Characteristics:

Age: 18 and over.

Performance status: ECOG 0 or 1.

Hematopoietic:

AGC at least 2,000.

Platelets at least 100,000.

Hepatic: Bilirubin no greater than 2.0 mg/dL

Renal: Creatinine no greater than 2.0 mg/dL

Cardiovascular:

No MI within the past year.

No active ischemic heart disease.

No NYHA class III/IV status.

No symptomatic arrhythmia.

OTHER:

No requirement for pharmacologic steroid doses for inflammatory or autoimmune disorders. Physiologic replacement doses of steroids allowed.

No concurrent cimetidine or oxypurinol.

No HIV antibody.

No history of seizure disorder.

No active infection or other serious concurrent medical illness that would preclude treatment.

No second malignancy within 3 years except curatively treated: In situ carcinoma of cervix, Basal cell carcinoma of the skin.

No pregnant or nursing women.

Effective contraception required of fertile patients.