PATIENT CHARACTERISTICS: Age: 18 and over Performance status: ECOG 0-2 Life expectancy: Not specified Hematopoietic: WBC at least 3,500/mm3 Platelet count at least 100,000/mm3 Hepatic: Not specified Renal: Creatinine clearance at least 30 mL/min Other: Must maintain adequate oral nutrition (i.e., at least 1200 calories estimated intake per day) No significant infection or other concurrent medical condition that would preclude study No significant nausea or vomiting No malabsorption secondary to short-gut syndrome, Crohn's disease, or sprue No patients with more than 6 bowel movements per day or baseline no greater than grade 3 diarrhea for patients with colostomy Not pregnant or nursing Negative pregnancy test Fertile patients must use effective contraception