Dosimetric aspects of vessel-sparing stereotactic radiation therapy for prostate cancer: prospective simulation study

INTRODUCTION: Тhe development of new methods of radical treatment of prostate cancer (PCa) aimed at maintaining a high quality of life is the most important task of modern oncourology. Radiation therapy with a dose reduction to the area of critical vascular erectile structures is one of them.

OBJECTIVE: Сompare different approaches for «vessel-sparing» stereotactic radiation therapy (VS-SRT) PCa.

MATERIALS AND METHODS: Тhe study included 20 patients with histologically confirmed PCa of low and intermediate risk of recurrence (NCCN). SRT was planed at five fractions of 7.25 Gy. During planning we ad to the standard critical organs, vascular structures that are responsible for erectile function (ErOAR)): penile bulb (PB), crura of the cavernous bodies (CCB) and internal pudendal arteries (IPA)). For each patient, four dosimetric plans (DP) were calculated: «vessel-sparing» (DP-VS); standard (DP-S); «vessel-sparing» plan calculated in the formation of the generally accepted anisotropic indent of 5 mm for the planned volume of irradiation and a step towards the rectum — 3 mm (DP-5/3); «vessel-sparing» plan for irradiation using a 0.5-centimeter multi-life collimator (DP-0.5). All dosimetry plans, with the exception of DP-0.5, were generated for a linear accelerator with a 0.25 cm multi-leaf collimator.

RESULTS: Аll dosimetry plans, were cherecterized by exellent target coverage abd meet the prescribed limits for the critical organs. Most efficient sparing of ErOAR was achieved in DP-VS. The advantages of DP-VS in comparison with DP-S was significant reduction (30%) of D2% for CCB (IPA) (р0.05).

DISCUSSION: Тhe obtained results indicate that VS-SRT is feasible in the vast majority of patients suffering from PCa. A significant reduction in the dose delivered to the ErOAR can be achieved at most linear electron accelerators equipped with modern multi-leaf collimators.

CONCLUSION: The greatest contribution to the reduction of radiation dose to ErOAR in VS-SRT PC is made by the reduction of standard PTV, while the width of the collimator leaf does not have a significant effect on the dose priscribed to this region.

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