DISEASE CHARACTERISTICS:

• Histologically or cytologically confirmed prostate cancer

  • Metastatic disease

    • Progressive disease despite androgen-deprivation therapy and antiandrogen withdrawal, defined by at least one of the following criteria:

      • Rising prostate-specific antigen (PSA) defined by 1 of the following criteria:

        • 3 consecutive rising PSA levels, with an interval of ≥ 2 weeks between each reading AND most recent reading ≥ 5 ng/mL within the past 2 weeks
        • PSA ≥ 20 ng/mL within the past year AND confirmed within the past 2 weeks
        • 50% rise in PSA within the past 6 months AND most recent reading ≥ 5 ng/mL within the past 2 weeks
      • Progression of bidimensionally measurable soft tissue (nodal metastasis) by CT scan or MRI of the abdomen and pelvis within the past 4 weeks

      • Progression of bone disease (evaluable disease)

        • New bone lesions by bone scan within the past 6 weeks
• PSA ≥ 5 ng/mL

• Testosterone < 50 ng/dL

  • Primary androgen deprivation with a luteinizing hormone-releasing hormone analogue must continue during study treatment if patient has not undergone orchiectomy
• No prostate cancer-related pain
• No visceral lung or liver metastasis
• No known brain metastases

PATIENT CHARACTERISTICS:

Age

• 18 and over

Performance status

• ECOG 0-2

Life expectancy

• More than 6 months

Hematopoietic

• Absolute neutrophil count ≥ 1,500/mm^3
• WBC ≥ 3,000/mm^3
• Platelet count ≥ 100,000/mm^3

Hepatic

• Bilirubin normal
• AST and ALT ≤ 2.5 times upper limit of normal (ULN)

Renal

• Creatinine ≤ 1.5 times ULN

Cardiovascular

• No symptomatic congestive heart failure
• No unstable angina pectoris
• No cardiac arrhythmia

Other

• Fertile patients must use effective contraception
• No ongoing or active infection
• No psychiatric illness or social situation that would preclude study compliance
• No other uncontrolled illness
• No other active malignancy within the past 2 years except nonmelanoma skin cancer

PRIOR CONCURRENT THERAPY:

Biologic therapy

• Not specified

Chemotherapy

• No prior chemotherapy for metastatic disease

Endocrine therapy

• See Disease Characteristics

Radiotherapy

• Prior radiotherapy allowed provided bone marrow function is adequate

Surgery

• See Disease Characteristics
• At least 4 weeks since prior major surgery

Other

• No more than 1 prior noncytotoxic therapy for metastatic disease
• No other concurrent commercial agents or therapies for the malignancy
• No other concurrent investigational agents

• No concurrent herbal, alternative, or food supplements (e.g., PC-SPES, saw palmetto, Hypericum perforatum [St. John's wort])

  • A daily multivitamin is allowed

• No initiation of bisphosphonate therapy immediately prior to or during study therapy

  • Concurrent bisphosphonates allowed provided dose is stable and was started ≥ 6 weeks ago and progressive disease has occurred