PATIENT CHARACTERISTICS: Age: 18 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 upper limit of normal (ULN) AST no greater than 1.5 times ULN No acute hepatitis Renal: Not specified Cardiovascular: No unstable cardiac disease No history of cardiac arrhythmia (treated or untreated) No new onset crescendo or rest angina (stable exertional angina allowed) Pulmonary: Not specified Other: Not pregnant or nursing Negative pregnancy test Fertile patients must use effective contraception at least 1 week prior to, during, and for at least 2 weeks after study No known hypersensitivity to fluorouracil-uracil or leucovorin calcium No grade 2 or greater nausea/vomiting or diarrhea No significant neurological or psychiatric condition, including psychotic disorders, dementia, or seizures No active serious infection or septicemia No severe gastrointestinal bleeding No other serious illness or significant medical condition that would preclude study No psychological, familial, or sociological condition that would preclude study