Inclusion Criteria

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)

- Aspartate aminotransferase (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)