DISEASE CHARACTERISTICS: Histologically confirmed adenocarcinoma of the prostate Any stage with an estimated risk of node involvement at least 15% (and therefore at significant risk for local and/or systemic failure) based on pretreatment PSA and Gleason score (GS), e.g.: GS of 7 and PSA greater than 7.5 ng/mL GS of 6 and PSA greater than 22.5 ng/mL GS of 5 and PSA greater than 37.5 ng/mL PSA greater than 4 and less than 100 ng/mL Highest pretreatment value determined by a monoclonal assay that has a normal range of 0-4 ng/mL PSA measured by polyclonal assay (e.g., Yang) that has a normal range of 0-2.5 ng/mL may need to be divided by a conversion factor of approximately 1.5 GS determination required prior to entry No distant metastases No biopsy proven lymph node involvement Ineligible for protocol RTOG-9408 (clinical stages T2c-T4 with GS of 6 or higher are eligible for this study)

PATIENT CHARACTERISTICS: Age: Any age Performance status: Karnofsky 70-100% Hematopoietic: Not specified Hepatic: Liver function tests no greater than 1.2 times normal Renal: Not specified Other: No major medical or psychiatric illness that would prevent completion of treatment or interfere with follow-up No second malignancy within 5 years except superficial nonmelanomatous skin cancer

PRIOR CONCURRENT THERAPY: Biologic therapy: Not specified Chemotherapy: No prior chemotherapy Endocrine therapy: At least 90 days since testosterone At least 60 days since finasteride Radiotherapy: No prior radiotherapy Surgery: No more than 60 days since surgical staging No radical surgery or cryosurgery