PATIENT CHARACTERISTICS: Age: Not specified Performance status: Karnofsky 70-100% Life expectancy: Not specified Hematopoietic: Absolute neutrophil count at least 1,000/mm3 Platelet count at least 100,000/mm3 Hepatic: Bilirubin less than 2.0 times upper limit of normal (ULN) SGOT less than 2.0 times ULN Alkaline phosphatase less than 2.0 times ULN Renal: Creatinine no greater than 1.5 mg/dL Other: Must be able to take oral medication