PATIENT CHARACTERISTICS: Age: 18 and over Performance status: ECOG 0-2 Life expectancy: At least 12 weeks Hematopoietic: Absolute neutrophil count at least 1,500/mm3 Platelet count at least 100,000/mm3 Hemoglobin at least 9.0 g/dL Hepatic: Bilirubin less than 1.5 times upper limit of normal (ULN) (unless documented Gilbert's syndrome) AST/ALT less than 3 times ULN (less than 5 times ULN if liver metastases present) Renal: Creatinine normal Cardiovascular: No unstable cardiovascular disease Other: No active, uncontrolled infection No other significant medical disorder or condition that would preclude study No other malignancy within the past 5 years except curatively treated nonmelanoma skin cancer or carcinoma in situ of the cervix Not pregnant or nursing Negative pregnancy test Fertile patients must use effective contraception