PATIENT CHARACTERISTICS: Age: 18 and over Performance status: ECOG 0-1 Life expectancy: Not specified Hematopoietic: WBC at least 3,000/mm3 OR Absolute neutrophil count at least 1,500/mm3 Platelet count at least 100,000/mm3 Hepatic: Bilirubin no greater than 1.5 times the upper limit of normal (ULN) AST and ALT no greater than 2 times ULN Renal: Creatinine no greater than 2.0 mg/dL Creatinine clearance at least 60 mL/min Cardiovascular: No New York Heart Association class III/IV heart disease No uncontrolled congestive heart failure or angina Pulmonary: No chronic obstructive pulmonary disease Gastrointestinal: No evidence of active gastrointestinal bleeding No active peptic ulcer disease No inflammatory bowel disease Other: Normal diet required No known active infections HIV negative AIDS-related complex (ARC) negative No substance abuse or psychiatric problems No evidence of autoimmune disease No other prior invasive malignancy except resected basal cell or squamous cell skin cancer Not pregnant or nursing Negative pregnancy test Fertile patients must use effective contraception