DISEASE CHARACTERISTICS:

• Histologically confirmed adenocarcinoma of the prostate

• Metastatic disease

  • Bone metastases by x-ray, bone scan, MRI, or biopsy

• Hormone-refractory disease (despite androgen deprivation and antiandrogen withdrawal if applicable) defined by at least 1 of the following criteria:

  • Progression of unidimensionally measurable disease within the past 28 days
  • Progression of evaluable but not measurable disease within the past 28 days
  • At least 2 consecutive increases in PSA taken at least 1 week apart

• Measurable or non-measurable disease

  • Soft tissue disease that has been irradiated within the past 2 months is not considered measurable disease
  • Soft tissue disease that has been irradiated 2 or more months prior to study is considered measurable disease if the lesion progressed after radiation
  • Must have at least 1 measurable lesion outside previously irradiated area to be considered measurable disease
• Must have been surgically or medically castrated
• No prior or concurrent, treated or untreated brain metastases

PATIENT CHARACTERISTICS:

Age:

• 18 and over

Performance status:

• Karnofsky 60-100%

Life expectancy:

• Not specified

Hematopoietic:

• Absolute granulocyte count at least 1,500/mm^3
• Platelet count at least 100,000/mm^3

Hepatic:

• Bilirubin no greater than upper limit of normal (ULN)
• AST and ALT no greater than 2 times ULN

Renal:

• Creatinine no greater than 1.5 mg/dL OR
• Creatinine clearance at least 60 mL/min

Other:

• Fertile patients must use effective contraception during and for 3 months after study
• Recovered from prior major infections
• No other significant active concurrent medical illness that would preclude study
• No other malignancy within the past 5 years except adequately treated basal cell or squamous cell skin cancer, carcinoma in situ of any site, or other adequately treated stage I or II cancer that is in complete remission

PRIOR CONCURRENT THERAPY:

Biologic therapy:

• No concurrent biological response modifiers

Chemotherapy:

• No more than 1 prior chemotherapy regimen
• At least 3 weeks since prior chemotherapy and recovered
• No concurrent chemotherapy

Endocrine therapy:

• See Disease Characteristics
• At least 4 weeks since prior flutamide or ketoconazole
• At least 6 weeks since prior bicalutamide or nilutamide
• Must continue any luteinizing hormone-releasing hormone (LHRH) agonist therapy (e.g., leuprolide or goserelin) started prior to study
• No concurrent corticosteroid or hormonal therapy (except LHRH agonist therapy)

Radiotherapy:

• See Disease Characteristics
• At least 3 weeks since prior radiotherapy and recovered
• At least 3 months since prior strontium chloride Sr 89 or samarium Sm 153 lexidronam pentasodium and recovered
• No concurrent radiotherapy

Surgery:

• See Disease Characteristics
• Recovered from any prior surgical procedures

Other:

• No concurrent bisphosphonates unless therapy began prior to study
• No concurrent unconventional therapy for malignancy (e.g., St. John's Wort, PC-SPES, or other herbal remedies)