RATIONALE: Androgens can cause the growth of prostate cancer cells. Drugs, such as triptorelin and flutamide, may stop the adrenal glands from making androgens. Radiation therapy uses high-energy x-rays to kill tumor cells. Giving triptorelin and flutamide together with radiation therapy may be an effective treatment for prostate cancer. It is not yet known whether giving triptorelin and flutamide together with external-beam radiation therapy is more effective than external-beam radiation therapy alone in treating prostate cancer. PURPOSE: This randomized phase III trial is studying triptorelin, flutamide, and external-beam radiation therapy to see how well they work compared to external-beam radiation therapy alone in treating patients with stage II or stage III prostate cancer.

OBJECTIVES: * Compare the impact of neoadjuvant androgen blockade therapy comprising triptorelin and flutamide followed by conformal external beam radiotherapy and continued androgen blockage therapy vs conformal external beam radiotherapy alone in patients with stage II or III prostate cancer. * Compare the survival rate, in terms of 5-year clinical or biological remission, in patients treated with these regimens. * Compare overall survival in patients treated with these regimens. * Compare acute and late toxicity of these regimens in these patients. * Compare quality of life of patients treated with these regimens. * Determine the value and time-delay to obtain prostate-specific antigen nadir in patients treated with external beam radiotherapy alone. OUTLINE: This is a randomized, multicenter study. Patients are randomized to 1 of 2 treatment arms. * Arm I: Patients undergo conformal external beam radiotherapy. * Arm II: Patients receive androgen blockade therapy comprising triptorelin subcutaneously every 4 weeks and oral flutamide once daily. Androgen blockade therapy continues for a total of 4 months. Two months after initiation of androgen blockade therapy, patients undergo conformal external beam radiotherapy. Quality of life is assessed. PROJECTED ACCRUAL: A total of 450 patients will be accrued for this study.