Inclusion Criteria:  Age ≥18 years Histologically proven adenocarcinoma of the prostate Low-risk or intermediate-risk prostate cancer according to NCCN risk categories (low risk: T1c-T2a, Gleason score ≤6, and PSA <10 µg/L; intermediate risk: T2b-T2c or Gleason score 7 or PSA 10-20 µg/L) Patients with pT1a/b tumor diagnosis after transurethral resection of the prostate (TURP) Domain score of 17-25 on the International Index of Erectile Function-5 (IIEF-5) questionnaire Karnofsky score of 70-100 Written informed consent  Exclusion Criteria:  Use of (neo-)adjuvant androgen deprivation therapy High-risk prostate cancer according to NCCN risk categories (T3a or Gleason score 8-10 or PSA >20 µg/L) Patients with "bulky" iT3 tumor diagnosis Previous pelvic irradiation or radical prostatectomy Clinical evidence of metastatic disease Patients who are unable to undergo MRI Patients who are incompetent to sign written informed consent