DISEASE CHARACTERISTICS: Histologically or cytologically confirmed adenocarcinoma of the prostate with lymphatic, bone, visceral or soft tissue metastases (stage IV) No prostatic transitional cell or small cell carcinoma PSA greater than 4.0 ng/dL Measurable or evaluable disease by PSA OR Bidimensional disease on physical exam or radiologic imaging studies Testosterone less than 50 mg/L if prior hormonal therapy with gonadal ablation (LHRH analogues) or estrogens No previously irradiated or new CNS metastases