ONE-SHOT Trial - Ultra-hypofractionated Single-dose SBRT for Prostate Cancer

Inclusion Criteria: * Written informed consent according to ICH/GCP regulations before registration and prior to any trial specific procedures * Histologically confirmed adenocarcinoma of the prostate without small cell features * Tumor clinical stage cT1c-2c, pN0 or cN0, M0, according to UICC TNM 2009 * MRI staging must confirm American Joint Committee on Cancer (AJCC) stage T1, T2a, T2b or T2c * Gleason score at biopsy 3+3 or 3+4 (WHO 2016 Grade Groups 1, 2) * PSA ≤15 ng/ml * WHO performance status 0-1 * International Prostate Symptom Score ≤ 10 (alpha blockers allowed) * MRI-based volume estimation of prostate gland ≤ 70 cc * Patient agrees not to father a child during trial treatment and during 6 months thereafter Exclusion Criteria: * Tumor clinical stage cT3a-3b or T4 * Evidence of T3a, T3b or T4 disease as assessed by MRI * Positive lymph-nodes or metastatic disease from prostate cancer on imaging studies. * Significant tumor on the transitional zone as assessed by MRI * Gleason at biopsy ≥ 4+3 * Androgen deprivation therapy or products known to affect PSA levels * Impossibility to implant Calypso beacons * History of hematologic or primary solid tumor malignancy, unless in remission for at least 3 years from registration with the exception of curatively treated localized non-melanoma skin cancer * Prior pelvic radiotherapy * Previous surgery for prostate cancer * Previous transurethral resection of the prostate (TURP) (\< 12 weeks before registration) * Hip prosthesis * Severe or active co-morbidity likely to impact on the advisability of SBRT * Any other serious underlying medical, psychiatric, psychological, familial or geographical condition, which in the judgment of the investigator may interfere with the planned staging, treatment and follow-up, affect patient compliance or place the patient at high risk from treatment-related complications