First Russian experience of the stereotactic radiotherapy on the prostate bed

Purpose. Assess the safety of postoperative radiation therapy on the area of the prostate bed (PB) using extreme dose hypofractionation (5 fractions of 6.67 Gr). Materials and methods. from April 2019 to March 2020 at the National Medical Center of Oncology named after N.N. Petrov of the Ministry of Health of the Russian Federation in the first 15 patients of the prostate cancer carried out stereotactic radiation therapy (SRT) on the PB. Depending on the clinical situation, adjuvant and salvage SRT were distinguished. Linear electron accelerators with 6 MeV energy are used for treatment. Three factional regimes were evaluated: 5 factions of 6.6 Gr, 5 factions of 6.8 Gr and 5 factions of 7 Gr. The clinical target volume is defined by RTOG (2010). Results. The median of follow-up was 7.6 (1.3-11.6) months. Of the 15 patients, adjuvant SRT performed three observed, and the remaining 12 patients salvage SRT (4 early, 8 delayed). Acute radiation toxicity was estimated in 12 patients. Early impairment from the lower urinary tract 1 degree was observed in 8 (66.7%) 12 of them. Toxicity of 2 or more degree in the early period was not observed. Clinical signs of early 1st degree toxicity from the rectum were found in five (41.7%) of the bowel of the 12 observed. One patient (8.3%) there was a mixture of blood in the feces, which required a medical correction, which was considered as toxicity of the 2nd degree. Conclusions. Postoperative SRT of the PB region is a promising modern method of radiation treatment of patients with prostate cancer. The presented methods of adjuvant and salvage SRT are feasible in clinical practice and are characterized by an acceptable level of early radiation toxicity.