DISEASE CHARACTERISTICS: Histologically diagnosed adenocarcinoma of the prostate Progressive metastatic or regional nodal disease after at least 4 weeks on flutamide, bicalutamide, or nilutamide, i.e.: Greater than 25% increase in sum of products of perpendicular diameters of all measurable lesions not previously irradiated OR Prostate-specific antigen (PSA) at least 5 ng/mL and risen from baseline on at least 2 successive occasions at least 2 weeks apart PSA progression required for "bone only" disease or disease that responded to androgen deprivation and is negative on imaging scans at entry Primary testicular androgen suppression with a luteinizing hormone-releasing hormone (LHRH) analogue plus antiandrogen or by orchiectomy required Intermittent LHRH analog/antiandrogen therapy resumed at least 4 weeks prior to and continued at time of entry LHRH analogue continued throughout study in absence of orchiectomy