PATIENT CHARACTERISTICS: Age: 18 and over Performance status: Karnofsky 60-100% Life expectancy: Not specified Hematopoietic: Absolute neutrophil count at least 1,500/mm3 Platelet count at least 100,000/mm3 Hemoglobin at least 10 g/dL Hepatic: Bilirubin less than 1.5 times upper limit of normal (ULN) SGOT and SGPT less than 3 times ULN Alkaline phosphatase less than 2 times ULN Renal: Creatinine less than 1.5 times ULN BUN less than 1.5 times ULN Other: No nonmalignant systemic disease that would cause patient to be a poor medical risk No acute infection requiring intravenous antibiotics No psychological disorder that would interfere with study compliance HIV negative No AIDS-related illness Not pregnant or nursing Negative pregnancy test Fertile patients must use effective contraception No frequent vomiting or medical condition that would interfere with oral medication intake (e.g., partial bowel obstruction) No prior or concurrent malignancy, except: Surgically cured carcinoma in situ of the cervix Basal or squamous cell skin cancer