Inclusion Criteria

DISEASE CHARACTERISTICS:

- Diagnosis of prostate adenocarcinoma

- Metastatic disease

- Must have failed initial hormonal therapy and have disease progression after at least
one chemotherapy regimen*, meeting any of the following criteria:

- Progressive PSA ≥ 5 ng/mL, as evidenced by 2 separate measurements taken ≥ 2
weeks apart with the second PSA measurement greater than the first one and PSA
measurement at screening greater than the first one

- Progressive measurable disease (e.g., changes in the size of lymph nodes or
parenchymal masses or appearance of new lesions on physical examination or
x-ray/CT scan) with a PSA level at screening ≥ 5 ng/mL

- Progressive bone metastasis (e.g., presence of new lesions on a bone scan) with
a PSA level at screening ≥ 5 ng/mL NOTE: *Prior chemotherapy must include a
taxane therapy, but disease progression does not have to follow taxane therapy

- Patients must maintain primary androgen ablation (hormonal) therapy AND experience
disease progression while not receiving antiandrogen therapy

PATIENT CHARACTERISTICS:

- ECOG performance status 0-1

- Life expectancy ≥ 6 months

- Absolute neutrophil count ≥ 1,500/mm^3

- Platelet count ≥ 100,000/mm^3

- WBC ≥ 3,500/mm^3

- Bilirubin ≤ 1.2 mg/dL

- Creatinine ≤ 1.5 mg/dL

- SGOT or SGPT ≤ 1.5 times upper limit of normal

- No other prior malignancy unless treated with curative intent and free of disease for
the time period considered appropriate for the specific cancer

- No uncontrolled hypertension

- No active infections

- No known HIV positivity

- No uncontrolled medical condition that would preclude study therapy

- No diagnosis of major depression or suicidal ideation

- No problems with oral absorption

PRIOR CONCURRENT THERAPY:

- See Disease Characteristics

- More than 4 weeks since prior surgery or radiotherapy and recovered

- At least 4 weeks since prior flutamide

- At least 6 weeks since prior bicalutamide

- No prior or concurrent herbal supplements or thiazide diuretics

- No other concurrent investigational or commercial agents or therapies