PATIENT CHARACTERISTICS: Age: 18 and over Performance status: ECOG 0 or 1 Life expectancy: Not specified Hematopoietic: Absolute neutrophil count greater than 1,500/mm3 Platelet count greater than 100,000/mm3 Hepatic: Bilirubin normal SGOT/SGPT no greater than 2.5 times upper limit of normal (ULN) (5 times ULN if documented liver metastases) Renal: Creatinine less than 2.5 mg/dL Other: Not pregnant or nursing Negative pregnancy test Fertile patients must use effective contraception during and for 3 months after study Adequate unassisted oral or adequate enteral intake to maintain reasonable state of nutrition No other concurrent medical condition that would preclude study therapy