PATIENT CHARACTERISTICS: Age: 18 and over Performance status: ECOG 0-2 Life expectancy: At least 12 weeks Hematopoietic: Absolute neutrophil count at least 2,000/mm3 Platelet count at least 150,000/mm3 Hemoglobin at least 9.0 g/dL Hepatic: Bilirubin no greater than 1.5 mg/dL regardless of liver tumor presence SGOT no greater than 3 times upper limit of normal (ULN) (5 times ULN if due to liver tumor) Renal: Creatinine no greater than 2.0 mg/dL Cardiovascular: No uncontrolled high blood pressure No unstable angina No symptomatic congestive heart failure No myocardial infarction within past 6 months No serious uncontrolled cardiac arrhythmia Gastrointestinal: No active inflammatory bowel disease No significant bowel obstruction No chronic malabsorption Other: Not pregnant or nursing Negative pregnancy test Fertile patients must use effective contraception No active infection HIV negative No AIDS related illness No significant alcoholism or substance abuse No severe medical or psychiatric illness that would preclude participation in study