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

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