DISEASE CHARACTERISTICS: Histologically or cytologically confirmed prostate carcinoma Metastatic disease Documented progression of prostate cancer while receiving androgen ablative therapy (i.e., surgical or chemical castration and a serum testosterone level in the castrate range) Documented hormone therapy resistance defined as: PSA rise on 3 occasions not less than 4 weeks apart Any evidence of progressive measurable disease PSA must be above 20 ng/mL prior to study entry No brain metastases