DISEASE CHARACTERISTICS: Histologically proven locally confined adenocarcinoma of the prostate Clinical stage T1c-T2b, NX or N0, M0 Gleason score 2-6 AND PSA greater than 10 ng/dL but no greater than 20 ng/dL OR Gleason score 7 AND PSA no greater than 20 ng/dL Prostate volume no greater than 60 mL by transrectal ultrasound prior to external beam radiotherapy American Urologic Association voiding symptoms score no greater than 18 No distant metastases