Inclusion Criteria

DISEASE CHARACTERISTICS:

- Histologically confirmed hormone-refractory adenocarcinoma of the prostate

- Disease progression while on prior luteinizing hormone-releasing hormone (LHRH)
analogues or after orchiectomy and antiandrogens, given concurrently or consecutively

- Disease progression is defined as PSA progression documented by increases in PSA
recorded at 2 consecutive measurements over a prior reference value

- Interval of at least 1 week between the reference value and the first of these
two PSA increases

- Continued elevation of PSA for at least 6 weeks after discontinuation of
antiandrogens

- Last PSA value at least 5 ng/mL (Hybritech equivalent)

- Must have serum testosterone less than 50 ng/mL and must continue on LHRH agonist
therapy if no prior surgical castration

- No symptomatic brain or leptomeningeal metastatic disease

PATIENT CHARACTERISTICS:

Age:

- Over 18

Performance status:

- ECOG 0-2

Life expectancy:

- Not specified

Hematopoietic:

- Neutrophil count at least 1,500/mm^3

- Platelet count at least 100,000/mm^3

Hepatic:

- Bilirubin less than 1.5 times upper limit of normal (ULN)

- ALT/AST no greater than 2.5 times ULN (5 times ULN if liver metastases present)

Renal:

- Creatinine no greater than 1.7 mg/dL

- No uncontrolled hypercalcemia

Cardiovascular:

- No history of severe heart disease

- No myocardial infarction within the past 6 months

- No cardiac insufficiency

- Normal cardiac function by MUGA scan and 12-lead EKG

Other:

- No other prior or concurrent malignancy except basal cell or squamous cell skin
cancer

- No uncontrolled systemic nonmalignant disease or infection

- No psychological, familial, or geographical conditions that would preclude compliance

PRIOR CONCURRENT THERAPY:

Biologic therapy:

- Not specified

Chemotherapy:

- At least 4 weeks since prior chemotherapy

Endocrine therapy:

- See Disease Characteristics

- No prior hormonal therapy except estramustine

- No concurrent estramustine

Radiotherapy:

- At least 4 weeks since prior radiotherapy

- No concurrent radiotherapy (e.g., for painful bone metastases)

Surgery:

- See Disease Characteristics

Other:

- No other concurrent experimental drugs or investigational therapy