PATIENT CHARACTERISTICS: Age: 18 and over Performance status: Karnofsky 70-100% Life expectancy: At least 6 months Hematopoietic: WBC at least 3,500/mm3 Platelet count at least 100,000/mm3 Hepatic: Bilirubin less than 2.0 mg/dL OR SGOT less than 3 times upper limit of normal Renal: Creatinine no greater than 2.0 mg/dL OR Creatinine clearance at least 40 mL/min Cardiovascular: No New York Heart Association class III-IV heart disease Pulmonary: No severe debilitating pulmonary disease Other: No other malignancy within past 5 years except nonmelanoma skin cancer No concurrent infection requiring antibiotics No narcotic dependent pain No positive stool guaiac excluding hemorrhoids No history of documented radiation induced proctitis No allergy to seafood