Partial or whole gland brachytherapy to maintain erections

INTERVENTION: Prostate brachytherapy either I125 (144 Gy) or HDR (1 x 19 Gy). Control arm: Whole gland brachytherapy Experimental arm: Hemigland brachytherapy CONDITION: Erectile dysfunction, Quality of life, Focal prostate brachytherapy, Late radiation effects, Oncologic efficacy ; ; PRIMARY OUTCOME: Deterioration of erectile function by assessment of the IIEF‐5 score. A drop of at least 5 points compared to baseline value or a need to start with a phosphodiesterase 5 inhibitor (PDE5 inhibitor) (or other medical interventions to improve erections) at last follow‐ up is considered as an event. SECONDARY OUTCOME: The incidence of late gastro‐intestinal (GI) and genito‐urinary (GU) toxicity (CTCAEv4 and IPSS) ; ; ; ; quality of life after treatment completion (EORTC QLQ‐C30 and PR25) ; ; ; ; Progression of local disease histologically and radiological. INCLUSION CRITERIA: 1. Histologically adenocarcinoma on template prostate biopsies (18‐26 cores according; Appendix A) [3]. 2. Unilateral significant tumor confirmed by histology (see point 4). 3. Clinical stage T1c‐T2b (Appendix B) 4. Gleason score 3 + 3 with =30% tumor of all taken cores (ISUP Grade Group 1), Gleason score 3 + 4 (ISUP Grade Group 2), and Gleason 4 + 3 (ISUP Grade Group 3) 5. PSA =15 ng/ml and Gleason 7 (Grade Group 2‐3) or PSA =20 ng/mL and Gleason 6 (Grade Group 1) 6. Baseline IIEF‐5 score =12 (Appendix C) 7. Sexually active by having intercourse 8. International Prostate Symptom Score (IPSS) = 20 (Appendix D) 9. WHO performance score = 2 (Appendix E) 10. Written informed consent