DISEASE CHARACTERISTICS: Histologically confirmed adenocarcinoma of the prostate Primary tumor confined to prostate TNM clinical Stages T1b-c or T2a-b No T1a No T1b-c tumor with Gleason grade 1-2/5 No Gleason grade 1-2/5 and PSA less than 4 ng/mL Nodes negative on imaging (Nx) or by surgical sampling (N0) PSA no greater than 15 ng/mL Treatment must begin within 28 days after randomization