DISEASE CHARACTERISTICS: Histologically confirmed hormone refractory prostate cancer Castrate serum testosterone levels less than 30 mg/dL occurring at least 4 weeks since prior flutamide or at least 6 weeks since prior bicalutamide Measurable or evaluable progressive disease Rising PSA involving two determinations (one at least 20 ng/mL if PSA is sole criterion) at least two weeks apart OR Increasing measurable or evaluable disease OR New metastasis

PATIENT CHARACTERISTICS: Age: Not specified Performance status: ECOG 0-2 Life expectancy: At least 3 months Hematopoietic: Absolute neutrophil count at least 1,500/mm3 Platelet count at least 100,000/mm3 Hepatic: Bilirubin no greater than 2.0 mg/dL No hepatic insufficiency Renal: Creatinine no greater than 2.0 mg/dL No renal failure Cardiovascular: Cardiac ejection fraction at least 50% by radionuclide ventriculogram No myocardial infarction within the past year No active angina No congestive heart failure No arrhythmias requiring medication Other: No active peptic ulcers No uncontrolled infection or other serious medical condition that would prevent compliance with chemotherapy No uncontrolled diabetes No spinal cord compression or carcinomatous meningitis

PRIOR CONCURRENT THERAPY: Biologic therapy: Not specified Chemotherapy: No prior chemotherapy No other concurrent chemotherapy Endocrine therapy: No concurrent corticosteroid therapy Concurrent gonadotropin-releasing hormone analogue allowed Radiotherapy: At least 2 months since prior radiotherapy (not to a measurable lesion) Concurrent palliative radiotherapy allowed Surgery: Not specified