Anatomical and topographical justification of "vessel-spare" radiation therapy of prostate cancer

Introduction. Currently, radiation therapy is one of the most effective and radical methods of treating prostate cancer (PCa), however, the specific gravity of radiation damage to the anatomical structures providing erectile function (EF) is not completely clear. The aim of this study was to investigate the anatomical and topographic relationship of the prostate and vascular structures that provide erectile function (EF), to substantiate the technique of «vascular-preserving» radiation therapy of prostate cancer (PCa). Materials and methods. The study included 50 patients with verified or suspected prostate cancer. All patients underwent multiparametric magnetic resonance imaging (mpMRI) with a magnetic field voltage of 1.5 T in accordance with the established protocol. The bulb of the penis, the legs of the cavernous corpora, and the internal genital artery were identified as critical vascular structures. The obtained images were analyzed using the Eclipse Planning System version 4.0 (Varian Medical System). Results. Appropriate visualization of critical structures of interest was achieved in all 50 patients. The volume of the bulb of the penis was 7.12 ± 2.91 (3.3-17.9) cm3. The average distance between the apex and bulb of the penis was 1.48 ± 0.42 (0.71-2.41) cm. In the vast majority of patients, this indicator exceeded 1 cm: up to 1 cm - in 8 (16%), from 1.1 up to 1.5 - in 19 (38%) and more than 1.51 cm - in 23 (46%) patients. The size of the apical cavernous distance was: 2.15 ± 0.39 (1.3-2.93) on the right, 2.2 ± 0.37 (1.49-2.91) cm on the left side. The internal genital artery in the general irradiated field (the prostate gland and the proximal third of the seminal vesicles) is at an average distance of 2.5 cm (gland apex) to 4.5 cm (gland base). Discussion. Modern radiotherapy of prostate cancer not only provides appropriate local control over the disease, but also has the technical capabilities to further optimizations. The maximal reduction in the radiation dose load on the patient’s reproductive organs vascular component based on the individual anatomy data makes it possible to maintain the initial status of erectile function at a high level. The obtained results show the practical feasibility of this approach. Conclusions. The anatomical and topographic relationships of the irradiated organs (prostate ± the proximal third of seminal vesicles) and critical vascular structures allow in the vast majority of cases (more than 80%) to perform «vascular preserving» version of radiation therapy.