Immediate results of perineal implantation of a prostate-rectum biodegradable spacer

Aim. To evaluate the immediate results of perineal implantation of a biodegradable spacer based on stabilized hyaluronic acid (SНA) of non-animal origin as a way to optimize radiation treatment of prostate cancer.Materials and methods. The study included 48 patients with verified low and intermediate risk prostate cancer per NCCN (National Comprehensive Cancer Network) who received five-fraction stereotactic radiotherapy as radical treatment. Prior to radiotherapy, all patients underwent insertion of a prostate-rectum biodegradable spacer (PRBS) based on synthetic SHA in the volume of 4–8 mL.Results. There were no allergic and inflammatory reactions of tissues to the chemical composition of the implanted PRBS. Despite the invasive nature of the procedure, we did not observe any cases of infectious complications.SНA used in the study demonstrated high levels of hydration (swelling) equal to 24.4 ± 1.5 (20.7–27.3) %, as well as temporal and spatial stability, which determined its optimal characteristics for use as a radiotherapeutic spacer. In all 48 patients, the projected distance (≥1 cm) between the prostate gland and the anterior wall of the rectum was achieved before the start of irradiation. The administration of 4 mL of SНA made it possible to achieve optimal symmetry of the formed space only in one (16.7 %) patient. An increase in the implant volume of the polymer to 6 mL increased the number of such cases to 28.6 %, and after injection of 8 mL it increased to 57 %.The use of PRBS made it possible to reduce radiation dose to the rectum from 21.5 % (D0.1cc (dose per 0.1 cm3 of rectum)) (р 0.0001) to 92.8 % (V75 % (volume receiving 75 % or more of the prescribed dose)) (р 0.0001). Dose reduction for one of the most clinically validated parameters – D2cc (dose to 2 cm3 of rectum)) was 31.5 % (р 0.0001) on average.Conclusion. Perineal implantation of a non-animal SНA (Russia) as a radiotherapy spacer in patients with prostate cancer demonstrates excellent safety and efficacy profiles.