Phase 1 : consists in a feasibility study (First 28 patients).~Phase 2 : monocentric prospective comparative cohort study.~Recruitment :~Centre intégré de cancérologie du CHU de Québec-Université Laval.~Recruitment period: December 2015 to June 2023~Brachytherapy :~Implantation under general or spinal anesthesia~Foley catheter insertion in bladder.~TRUS prostate localisation.~Prostate volume measurement.~Gold fiducial markers (3) insertion.~Prostate brachytherapy catheters (14 à 21) insertion.~Cystoscopy for bladder and urethra integrity control.~Re-insertion of foley catheter after cystoscopy.~Planning imaging: TRUS or CT scan (has needed).~Structures delineation by radiation oncologist (brachytherapist).~Prostate~Seminale vesicles~Rectum~Colon sigmoïde~Bladder~Urethra~Penile bulb~Dosimetric optimisation~Oncentra Prostate v. 4.2.2 d'Elekta brachytherapy (Veenendaal, The Netherlands)~Oncentra Brachy version 4.6 (if under CT scan).~Treatment (brachytherapy dose delivery).~15 Gy in one fraction~Direct interstitial dose monitoring (20 patients or more). Fiber-optic dosimeter inserted in prostate brachytherpy catheter for live dose delivery mesurements.~Foley ablation under full bladder, same day or day after therapy.~Radiotherapy:~Via IMRT, VMAT or SBRT technics.~Dose : 25 Gy in 5 fractions administered over a 7 days period. 2 to 3 fractions separated by 2 days, weekend break.~PTV includes prostate and the first centimeter of seminal vesicle.~Simulation~one week post brachytherapy~standard has described in the department procedure manual.~maximal CT scan slice thickness : 2-3mm.~uretro-graphy done to identify urogenital sphincter.~Multiparametric MRI~If no counter-indication and available,~a T2 tridimensional sequence for prostate delineation~slice thickness : 1 mm.~a diffusion weighted sequence will be done.~a DTI with tractography can be done optionally.~contrast media (gadolinium) is optional.~Physique~Linac energy (between 6 MV to 18 MV).~ARC therapy technique will be used~planification softwares: Éclipse, Pinnacle or Raystation.~Portal (kV-kV) imagery will be used for marker match.~CBCT will be done at each fraction delivered.~Clinical and dosimetric data will be collected prior treatment.~Primary objectives :~Toxicity analysis will be quantitatively evaluated using CTCAE (v5) at 1, 2 and 5 years post-therapy, and has needed at FU visits. Kaplan-Meier statistical analysis will be used to report toxicity evolution through time.~median IPSS scores will be reported at 3, 6, 12 months and yearly (1, 2, 3, 4 et 5) post-therapy. IPSS median time to baseline return will be calculated.~IPSS urinary scores, sexual function (SHIM) and GI toxicity (CTCAE-v5) and quality of life questionnaires ( EPIC-26) will be given at 3, 6 months and yearly thereafter (1, 2, 3, 4 et 5) post-treatment.~Secondary objectives : Biochemical disease-free survival has per Phoenix definition (by American Society of Radiation Oncology - ASTRO) recommendation will be reported using Kaplan-Meier analysis.
Phase 1-2 study, comparing ultra-hypofractionnated (UH) to a moderately hypofractionnated (MH) radiation therapy, with image guided HDR prostate brachytherapy. Using iso-equivalent doses, a non-inferiority analysis will be done in order to prove UH non-inferior to MH, toxicity wise. Acceptability, tolerability, acute and late toxicity will be reported. MRI visible dominant intra-prostatic lesion will be outlines and variability between radiation oncologists and radiologists will be reported. As secondary objective, biochemical and clinical failure free survival will be reported at 5 & 10 years.