PRIOR CONCURRENT THERAPY: Biologic therapy: Not specified Chemotherapy: At least 6 weeks since prior cytotoxic chemotherapy Endocrine therapy: At least 6 weeks since prior adrenal hormone inhibitors or corticosteroid therapy Antiandrogen therapy must be discontinued prior to measuring PSA values Luteinizing hormone-releasing hormone analog must be maintained during study OR must be discontinued at least 10 weeks prior to study entry (for 28 day depot preparation) or 24 weeks prior to study entry (for 3 month depot preparation) Radiotherapy: At least 6 weeks since prior radiotherapy Surgery: Not specified