Single-Dose Image-Guided Radiotherapy With Urethral Sparing and DIL Boost for Intermediate-Risk Prostate Cancer (PROSINT II)

Inclusion criteria Participants must meet all of the following criteria: Signed study-specific informed consent form Histologic confirmation of adenocarcinoma of the prostate by biopsy Biopsy ISUP grade 1-3 Biopsy-proven localized intermediate-risk prostate cancer according to NCCN criteria No previous hormonal therapy PSA ≤20 ng/mL Staging multiparametric MRI confirmation of AJCC cT1c-cT2c disease, with no radiographic evidence of cT3, cT4, or N1 disease No direct evidence of regional or distant metastases after appropriate staging studies Age ≥18 years Performance status 0-2 IPSS score ≤15; alpha-blockers allowed CT- or ultrasound-based prostate gland volume estimate ≤100 grams Exclusion criteria Participants with any of the following are ineligible: Positive lymph nodes or metastatic disease from prostate cancer on imaging studies MRI evidence of radiographic T3, T4, or N1 disease Biopsy ISUP grade ≥4 Previous pelvic radiotherapy Previous surgery for prostate cancer Previous transurethral resection of the prostate within 3 months Contraindication to protocol-required Foley catheter placement, rectal-balloon placement, MRI, PSMA PET/CT where required, or treatment immobilization/tracking procedures Active urinary tract infection, unresolved acute prostatitis, or other acute condition judged by the investigator to make simulation or SDRT unsafe until resolved Previous hormonal therapy History of Crohn's disease or ulcerative colitis Previous significant obstructive symptoms Significant psychiatric illness CT- or ultrasound-estimated prostate volume \>100 grams Severe active comorbidity judged by the investigator to preclude protocol treatment