Inclusion Criteria

DISEASE CHARACTERISTICS: Histologically confirmed metastatic colorectal adenocarcinoma
Measurable disease

PATIENT CHARACTERISTICS: Age: 75 and over Performance status: ECOG 0-2 Life expectancy:
Not specified Hematopoietic: Absolute neutrophil count at least 1,500/mm3 Platelet count
at least 100,000/mm3 Hepatic: Bilirubin no greater than 1.5 mg/dL AST or ALT no greater
than 2.5 times upper limit of normal (ULN) Renal: Creatinine no greater than 1.5 times ULN
Other: No serious infection No other serious underlying medical condition that would
preclude protocol therapy No known hypersensitivity to fluorouracil-uracil or leucovorin
calcium

PRIOR CONCURRENT THERAPY: Biologic therapy: At least 6 months since prior adjuvant
immunotherapy for colorectal cancer No concurrent immunotherapy Chemotherapy: At least 6
months since prior adjuvant chemotherapy for colorectal cancer No other concurrent
chemotherapy Endocrine therapy: No concurrent hormonal therapy Radiotherapy: See Disease
Characteristics At least 6 months since prior adjuvant radiotherapy for colorectal cancer
Prior radiotherapy for locally symptomatic disease allowed Surgery: Prior surgery allowed
Other: No prior therapy for metastatic disease No other concurrent investigational drugs
No concurrent halogenated antiviral agents (e.g., lodenosine, fialuridine, FMAU,
emtricitabine, and sorivudine)