DISEASE CHARACTERISTICS:

• Histologically confirmed adenocarcinoma of the prostate

  • Metastatic disease (N1 and/or M1)
• Disease unresponsive or refractory to androgen-deprivation therapy
• Must have received only 1 prior chemotherapy regimen comprising a taxane OR mitoxantrone

• Disease progression as defined by one or more of the following:

  • Progression of measurable disease

    • Prior radiotherapy allowed provided radiotherapy was completed ≥ 2 months ago and lesion progressed since radiotherapy

  • Progression of nonmeasurable disease

    • Prior radiotherapy within the past 2 months allowed, but disease is considered nonmeasurable

  • Rising prostate-specific antigen (PSA) after > 2 courses of chemotherapy OR within 6 months of last chemotherapy dose

    • Rising PSA defined as at least 2 consecutive rises in PSA to be documented over a reference value (measure 1)
• PSA ≥ 5 ng/mL

• Surgical or medical castration required

  • Castration using luteinizing hormone-releasing hormone agonist (leuprolide acetate or goserelin) or antagonist (abarelix) should not be interrupted

• No history of brain metastases OR currently treated or untreated brain metastases

  • Patients with clinical suspicion of brain metastases must have a brain CT scan or MRI negative for metastatic disease within the past 56 days

PATIENT CHARACTERISTICS:

• Zubrod performance status 0-2
• Fertile patients must use effective contraception
• Absolute granulocyte count ≥ 1,500/mm³ (transfusion independent)
• Platelet count ≥ 100,000/mm³ (transfusion independent)
• Hemoglobin ≥ 9 g/dL (transfusion independent)
• Creatinine clearance ≥ 40 mL/min
• Bilirubin ≤ 2 times upper limit of normal (ULN)
• AST ≤ 2 times ULN

• No uncontrolled intercurrent illnesses including, but not limited to, the following:

  • Diabetes mellitus
  • Ongoing or active infection
  • Symptomatic congestive heart failure
  • Unstable angina pectoris
  • Cardiac arrhythmia
• No psychiatric illness or social situation that would preclude study compliance
• No known HIV positivity

• No other prior malignancy except for the following:

  • Adequately treated basal cell or squamous cell skin cancer
  • Adequately treated stage I or II cancer in complete remission
  • Any other cancer from which the patient has been disease-free for 5 years

PRIOR CONCURRENT THERAPY:

• See Disease Characteristics
• At least 21 days since prior surgery and recovered
• At least 28 days since prior chemotherapy and recovered
• At least 28 days since prior flutamide or ketoconazole

• At least 28 days since prior radiotherapy (to < 30% of the bone marrow only) and recovered

  • Prior samarium Sm 153 lexidronam pentasodium allowed
  • No prior strontium chloride Sr 89
• At least 42 days since prior bicalutamide or nilutamide
• More than 60 days since prior murine or chimeric proteins or human/murine monoclonal antibody

• Concurrent bisphosphonate therapy allowed provided the following are true:

  • Therapy commenced at least 3 weeks ago
  • Therapy continues for the entire duration of study treatment
• No other concurrent anticancer therapy, including cytotoxic therapy, biologic therapy, radiotherapy, or hormonal therapy (except for luteinizing hormone-releasing hormone agonist or antagonist in patients who have not had an orchiectomy)