Single Fraction Early Prostate Irradiation (SiFEPI)

Inclusion Criteria: * Patients suffering from histologically-proven adenocarcinoma-type prostate cancer: * with low risk of biochemical recurrence * with a low intermediate risk of biochemical recurrence (maximum of 1 intermediate risk factor)\* * stage T1c, T2a, T2b * Gleason score 6 (3+3) or 7 (3+4) with at most 3 positive biopsies * PSA \< 15 ng/ml * Age ≥ 18 years * Karnofsky index ≥ 70% * Life expectancy ≥ 10 years * No contraindication to injection of hyaluronic acid in the prostate-rectal interspace * Patient aware of the information leaflet and having signed the informed consent form * Patient covered by medical insurance Exclusion Criteria: * Stage ≥ T2c * Gleason score 7 (4+3) or ≥ 8 * PSA \> 15 ng/ml * Presence of the following anatomico-pathological criteria: * Involvement of the nerve fibers * Peri-tumoral vascular embolisms * Capsule involvement * Number of positive biopsies ≥ 50% * 100% positive biopsies in a lobe * Involvement of the seminal vesicle * Prostate volume ≥60 cc * Large prostatic transurethral resection and/or dating from less than 6 months * Poor urinary function in the absence of alpha-blockers * IPSS score \> 15 * Post-mictional residue \> 50 cc * Flow rate with Qmax \< 12 ml/s * Remote metastasis * Neoadjuvant anti-androgenic treatment * Prior treatment with pelvic irradiation and/or chemotherapy * Active infection or other underlying severe pathology likely to prevent the patient from receiving treatment * Histo…