DISEASE CHARACTERISTICS: Histologically confirmed adenocarcinoma of the prostate with progressive systemic disease despite at least 1 endocrine manipulation including 1 of the following: Orchiectomy LHRH analogue with or without flutamide, megestrol, or diethylstilbestrol Flutamide must be discontinued for at least 2 weeks with PSA stabilized above normal or rising Measurable or evaluable disease No brain metastasis

PATIENT CHARACTERISTICS: Age: Not specified Performance status: ECOG 0-2 Life expectancy: Greater than 2 months Hematopoietic: Granulocyte count at least 1,500/mm3 Platelet count at least 100,000/mm3 Hepatic: Bilirubin greater than 1 mg/dL SGOT greater than 2 times upper limit of normal Renal: Creatinine less than 2 mg/dL Hydronephrosis with impaired renal function must be decompressed adequately Cardiovascular: No severe cardiac (i.e., symptomatic arrhythmia requiring medication or active congestive heart failure) or coronary disease that are unstable despite medication Other: Adequate nutritional status (at least 1,500 Kcal/day) No other significant active medical illness that would preclude study therapy or survival No other malignancy within the past 5 years except adequately treated basal or squamous cell carcinoma of the skin No acute spinal cord compression

PRIOR CONCURRENT THERAPY: Biologic therapy: No concurrent biologic response modifiers Chemotherapy: No other concurrent chemotherapy Endocrine therapy: See Disease Characteristics At least 2 weeks since prior corticosteroids No concurrent exogenous corticosteroids except for documented CNS metastases or adrenal insufficiency Concurrent hormones for nondisease conditions allowed (e.g., insulin for diabetes mellitus) Concurrent continuation of monthly hormonal therapy with an LHRH agonist or DES required Radiotherapy: Prior radiation to symptomatic metastatic site allowed provided it is not the only measurable or evaluable lesion At least 2 weeks since prior radiotherapy and recovered No concurrent radiotherapy No concurrent palliative radiotherapy except for whole brain irradiation for documented CNS disease or impending spinal cord compression Surgery: See Disease Characteristics At least 3 weeks since prior surgery and recovered Other: No other concurrent treatment for prostate cancer except pain palliation