PATIENT CHARACTERISTICS: Age: 18 and over Performance status: SWOG 0-1 Life expectancy: At least 12 weeks Hematopoietic: Absolute granulocyte count at least 1,500/mm3 Platelet count at least 100,000/mm3 Hemoglobin at least 9 g/dL No coagulation disorders Hepatic: Bilirubin normal AST and ALT no greater than 3 times upper limit of normal (ULN) (no greater than 5 times ULN if liver involvement) Renal: Creatinine less than 1.5 mg/dL Creatinine clearance at least 45 mL/min Cardiovascular: No cardiac conduction abnormalities Other: Not pregnant or nursing Negative pregnancy test Fertile patients must use effective contraception No active infection No concurrent serious systemic disorders No concurrent or recent (within past 6 months) small bowel obstruction, symptoms of small bowel obstruction, or any other gastrointestinal disease