PATIENT CHARACTERISTICS: Age: 15 and over Performance status: ECOG 0-2 Life expectancy: At least 12 weeks Hematopoietic: Absolute neutrophil count at least 1,500/mm3 Platelet count greater than 100,000/mm3 Hepatic: Bilirubin no greater than 1.5 mg/mL SGOT/SGPT no greater than 2 times upper limit of normal Renal: Creatinine no greater than 1.5 mg/mL OR Creatinine clearance at least 60 mL/min Cardiovascular: At least 6 months since any acute myocardial infarction No congestive heart failure No New York Heart Association class III or IV heart disease No clinically significant cardiac arrhythmias Pulmonary: Not specified Other: Not pregnant or nursing Fertile patients must use effective contraception No gastrointestinal bleeding or bleeding tendency