PATIENT CHARACTERISTICS: Age: 18 and over Performance status: ECOG 0 or 1 Hematopoietic: (within 2 weeks prior to entry) WBC at least 4,000/mm3 Platelet count at least 100,000/mm3 Hepatic: (within 2 weeks prior to entry) Bilirubin no greater than 2.0 mg/dL AST no greater than twice normal Renal: (within 2 weeks prior to entry) Creatinine no greater than 1.5 mg/dL OR Creatinine clearance greater than 40 mL/min Other: No active unresolved infection No concurrent parenteral antibiotics At least 7 days since parenteral antibiotics No history of prior malignancy within 5 years except: Curatively treated nonmelanomatous skin cancer In situ cancer of the cervix Not pregnant or nursing Adequate contraception required of fertile patients Physically and medically able to take oral medications