PATIENT CHARACTERISTICS: Age: 18 and over Performance status: Eastern Cooperative Oncology Group (ECOG) 0-2 Life expectancy: Not specified Hematopoietic: white blood count (WBC) greater than 3,000/mm3 Platelet count greater than 150,000/mm3 Hemoglobin at least 10 g/dL (transfusions and/or epoetin alfa allowed if stable without treatment for at least 1 week) Hepatic: Bilirubin less than 1.5 times upper limit of normal (ULN) SGOT or SGPT no greater than 5 times ULN Renal: Creatinine less than 1.5 times ULN Other: Not pregnant or nursing Negative pregnancy test Fertile patients must use effective barrier contraception No poor medical risks because of nonmalignant systemic disease No active uncontrolled infection No intractable vomiting (e.g., grade 2 or higher despite antiemetics) or any medical condition that could preclude taking oral medication and gastrointestinal absorption No AIDS related illness HIV negative