<br>        DISEASE CHARACTERISTICS:<br><br>          -  Histologically confirmed hormone-refractory adenocarcinoma of the prostate<br><br>          -  Disease progression while on prior luteinizing hormone-releasing hormone (LHRH)<br>             analogues or after orchiectomy and antiandrogens, given concurrently or consecutively<br><br>          -  Disease progression is defined as PSA progression documented by increases in PSA<br>             recorded at 2 consecutive measurements over a prior reference value<br><br>               -  Interval of at least 1 week between the reference value and the first of these<br>                  two PSA increases<br><br>          -  Continued elevation of PSA for at least 6 weeks after discontinuation of<br>             antiandrogens<br><br>          -  Last PSA value at least 5 ng/mL (Hybritech equivalent)<br><br>          -  Must have serum testosterone less than 50 ng/mL and must continue on LHRH agonist<br>             therapy if no prior surgical castration<br><br>          -  No symptomatic brain or leptomeningeal metastatic disease<br><br>        PATIENT CHARACTERISTICS:<br><br>        Age:<br><br>          -  Over 18<br><br>        Performance status:<br><br>          -  ECOG 0-2<br><br>        Life expectancy:<br><br>          -  Not specified<br><br>        Hematopoietic:<br><br>          -  Neutrophil count at least 1,500/mm^3<br><br>          -  Platelet count at least 100,000/mm^3<br><br>        Hepatic:<br><br>          -  Bilirubin less than 1.5 times upper limit of normal (ULN)<br><br>          -  ALT/AST no greater than 2.5 times ULN (5 times ULN if liver metastases present)<br><br>        Renal:<br><br>          -  Creatinine no greater than 1.7 mg/dL<br><br>          -  No uncontrolled hypercalcemia<br><br>        Cardiovascular:<br><br>          -  No history of severe heart disease<br><br>          -  No myocardial infarction within the past 6 months<br><br>          -  No cardiac insufficiency<br><br>          -  Normal cardiac function by MUGA scan and 12-lead EKG<br><br>        Other:<br><br>          -  No other prior or concurrent malignancy except basal cell or squamous cell skin<br>             cancer<br><br>          -  No uncontrolled systemic nonmalignant disease or infection<br><br>          -  No psychological, familial, or geographical conditions that would preclude compliance<br><br>        PRIOR CONCURRENT THERAPY:<br><br>        Biologic therapy:<br><br>          -  Not specified<br><br>        Chemotherapy:<br><br>          -  At least 4 weeks since prior chemotherapy<br><br>        Endocrine therapy:<br><br>          -  See Disease Characteristics<br><br>          -  No prior hormonal therapy except estramustine<br><br>          -  No concurrent estramustine<br><br>        Radiotherapy:<br><br>          -  At least 4 weeks since prior radiotherapy<br><br>          -  No concurrent radiotherapy (e.g., for painful bone metastases)<br><br>        Surgery:<br><br>          -  See Disease Characteristics<br><br>        Other:<br><br>          -  No other concurrent experimental drugs or investigational therapy<br>