Feasibility Trial of Single-Dose Radiotherapy for Localized Low and Intermediate Risk Prostate Cancer

The goal of this study is to assess the feasibility of high-dose radiotherapy (Single-Dose Radiotherapy, SDRT) of 24 Gy in patients with localized low and intermediate risk prostate cancer using a special system of internal and external immobilization of the prostate gland. Patients eligible for this study are classified according to the National Comprehensive Cancer Network (NCCN) guidelines as low or intermediate risk prostate cancer (Stage T1-T2c and/or Prostate Specific Antigen (PSA) level ≤20 ng/mL and/or Gleason score of ≤7). The study will examine the technical feasibility of image-guided volumetrically-modulated arc therapy (VMAT-IGRT) with an emphasis on normal tissue sparing and precision of radiation delivery using dedicated devices (an air-filled endorectal balloon and a Foley catheter) that ensure target immobilization and reproducibility of prostate anatomical localization using a special external patient immobilization system, including patient placement on the patient transfer trolley, which allows patient transfer without removing the endorectal balloon and urinary catheter during all stages of simulation and treatment planning (MR, CT, Positron emission tomography (PET) / CT-simulation) and during the treatment session on the linear accelerator. Previously untreated patients with localized prostate cancer of the low risk and favorable intermediate risk (NCCN) groups will receive SDRT at a dose of 24 Gy. In patients from the unfavourable intermediate risk (NCCN) group with a visible dominant intraprostatic lesion (DIL), local escalation of the DIL dose to 30 Gy will be performed. Patients will be followed up at one week and one month after completion of treatment, then every 3 months for 24 months (+/- 4 weeks), and every 6 months thereafter. Evaluation of early and late adverse events will focus, although not exclusively, on the genitourinary and gastrointestinal toxicity, primarily the rectal toxicity. Serum prostate-specific antigen (PSA) levels will be determined according to the clinical follow-up schedule. Multiparametric magnetic resonance imaging (mpMRI) with intravenous contrast will be performed at baseline and at 6-, 12-, and 24-months post-intervention. Participants of the study will be followed up for at least 2 years after treatment.