DISEASE CHARACTERISTICS: Histologically confirmed hormone refractory prostate cancer Castrate serum testosterone levels less than 30 mg/dL occurring at least 4 weeks since prior flutamide or at least 6 weeks since prior bicalutamide Measurable or evaluable progressive disease Rising PSA involving two determinations (one at least 20 ng/mL if PSA is sole criterion) at least two weeks apart OR Increasing measurable or evaluable disease OR New metastasis