PRIOR CONCURRENT THERAPY: Biologic therapy: Not specified Chemotherapy: Not specified Endocrine therapy: See Disease Characteristics At least 6 months since prior hormonal therapy Radiotherapy: See Disease Characteristics No more than 10 permanent radioactive seed implants Less than 1 cm from prostate apex or less than 1.2 cm from rectal wall Surgery: At least 6 weeks since prior transurethral resection of the prostate or other prostate surgery No prior rectal surgery except hemorrhoidectomy Other: No definitive local treatment for prostate cancer since completion of external beam radiotherapy At least 2 months since prior finasteride or other agents that affect PSA (e.g., saw palmetto) At least 3 months since prior benign prostatic hypertrophy thermotherapy or hyperthermia treatment At least 30 days since prior investigational drug or device No concurrent participation in another clinical trial