PATIENT CHARACTERISTICS: Age: 18 and over Performance status: ECOG-WHO 0-2 Life expectancy: At least 12 weeks Hematopoietic: Absolute neutrophil count greater than 1,500/mm3 Platelet count at least 100,000/mm3 Hemoglobin at least 9.0 g/dL Hepatic: Bilirubin no greater than 2.0 mg/dL SGOT or SGPT no greater than 3 times upper limit of normal (ULN) (5 times ULN if elevations due to liver metastasis) Renal: Creatinine no greater than 1.5 times ULN Cardiovascular: No prior or concurrent QTc interval prolongation greater than 500 m/sec, unless approved by cardiology consult prior to study Other: No malabsorption syndrome due to surgery, prior disease, or other unknown reason No frequent vomiting or other medical condition that could interfere with oral medicine intake (e.g., partial bowel obstruction, external biliary diversion) No concurrent nonmalignant systemic disease making patient a poor risk for study No active uncontrolled infection Not pregnant or nursing Negative pregnancy test Fertile patients must use effective contraception