Radiation Therapy in Treating Patients With Stage I, Stage II, or Stage III Prostate Cancer

RATIONALE: Radiation therapy uses high-energy x-rays to damage tumor cells. It is not yet known whether radiation therapy to the prostate and pelvis is more effective than radiation therapy to the prostate alone in treating prostate cancer. PURPOSE: Randomized phase III trial to compare the effectiveness of radiation therapy to the prostate with or without radiation to the pelvis in treating patients with stage I, stage II, or stage III prostate cancer.