PATIENT CHARACTERISTICS: Age: 18 and over Performance status: Karnofsky 60-100% Life expectancy: Greater than 24 months Hematopoietic: Not specified Hepatic: SGOT and SGOT no greater than 2.5 times upper limit of normal Renal: Creatinine no greater than 2.0 mg/dL Cardiovascular: No severe cerebrovascular disease or sustained hypotension not secondary to antihypotensive medication Other: No history of inflammatory bowel disease No history of malignancy other than nonmelanoma skin cancer No underlying medical or psychiatric illness that may impair ability to participate in study