DISEASE CHARACTERISTICS: Histologically or cytologically confirmed metastatic hormone refractory prostate cancer Disease progression after orchiectomy or during hormonal therapy Measurable or evaluable disease At least 2 consecutive increases in PSA At least 1 week between reference value and first increase OR Third value must be higher than second if second value is less than reference value PSA at least 5 ng/mL No leptomeningeal or brain metastases