Stereotactic Radiotherapy of Prostate Cancer With Reduction of Safety Margins

In this prospective study, a total of 100 patients will be treated over 2 years. Patients will be implanted with 4 contrast markers (fiducials) in the prostate - in the base, apex, and right and left lobes of the prostate. Subsequently, 3 planning examinations will be performed: 1. CT with a urinary catheter immediately after the implantation of fiducials (gold contrast markers), with a distance from implantation 2. planning CT and MR without a urinary catheter. The CTV (Clinical Target Volume) will be defined by the prostate, and the border on the PTV will be reduced from 3-5 mm to 1-2 mm isometrically to maximize the reduction of doses to the organs at risk (rectum, bladder, and urethra, penile bulb, testes), the organs at risk (OAR) will be marked in the radiation plan as OAR. Subsequently, the patients will be irradiated with a dose of 36.25 Gy in 5 fractions per day. Acute toxicity will be evaluated in the 1st and 3rd month after radiotherapy, and late toxicity after 4-6 months according to CTCAE criteria (Common Terminology Criteria for Adverse Events).