PATIENT CHARACTERISTICS: Age: 18 and over Performance status: ECOG 0-1 Menopausal status: Not specified Life expectancy: Not specified Hematopoietic: WBC at least 3,000/mm3 Absolute neutrophil count at least 1,500/mm3 Hemoglobin at least 9 g/dL (transfusion or epoetin alfa allowed) Platelet count at least 100,000/mm3 Hepatic: SGOT/SGPT no greater than 1.5 times upper limit of normal (ULN) Albumin at least 3.0 g/dL Bilirubin no greater than 1.5 times ULN Renal: Creatinine no greater than 1.5 times ULN Creatinine clearance at least 60 mL/min Other: No other active malignancy except nonmelanoma skin cancer Not pregnant or nursing Fertile patients must use effective contraception No inflammatory bowel disease or active gastric ulcer No prior autoimmune disease or immunodeficiency syndrome