Radiation Therapy in Treating Patients Receiving Hormone Therapy for Prostate Cancer (GETUG-AFU 18)

RATIONALE: Radiation therapy uses high-energy x-rays to kill tumor cells. Specialized radiation therapy that delivers a high dose of radiation directly to the tumor may kill more tumor cells and cause less damage to normal tissue. It is not yet known which dose of radiation therapy is more effective in treating patients with prostate cancer. PURPOSE: This randomized phase III trial is comparing two radiation therapy regimens in treating patients with prostate cancer receiving hormone therapy.

DISEASE CHARACTERISTICS: * Histologically confirmed adenocarcinoma of the prostate * Unfavorable disease, defined by at least 1 of the following criteria: * Clinical stage T3 or T4 * Gleason score ≥8 * Serum prostate-specific antigen (PSA) ≥20 ng/mL and ≤100 ng/mL * pN0 disease allowed if lymphadenectomy performed before patient began hormone therapy * No pelvic lymph nodes ≥15 mm by CT scan or MRI * No axillary lymph node involvement (pN1) * No bone metastasis * Must be starting hormonal treatment on or up to 6 months before beginning radiotherapy PATIENT CHARACTERISTICS: * Eastern Cooperative Oncology Group (ECOG) performance status 0-1 * Life expectancy \>5 years * Must be enrolled in a social security program * No other cancer, except basal cell skin cancer, that has been treated or relapsed within the past 5 years * No severe uncontrolled hypertension (systolic BP ≥160 mm Hg or diastolic BP ≥90 mm Hg) * No contraindication to luteinizing hormone-releasing hormone agonists * No contraindication to pelvic irradiation (e.g., scleroderma, chronic inflammatory gastrointestinal disease) * No hip prosthesis * Must not be deprived of liberty or under guardianship * No geographical, social, or psychological reasons that would preclude follow up PRIOR CONCURRENT THERAPY: * See Disease Characteristics * No prior pelvic irradiation * At least 3-4 months since prior transurethral resection * No other prior surgery for prostate cancer * No concurrent participation in another clinical trial which would require approval upon entry to this trial