Dosimetric feasibility of neurovascular bundle-sparing stereotactic body radiotherapy with periprostatic hydrogel spacer for localized prostate cancer to preserve erectile function

Abstract

Objective: We aim to test the hypothesis that neurovascular bundle (NVB) displacement by rectal hydrogel spacer combined with NVB delineation as an organ at risk (OAR) is a feasible method for NVB-sparing stereotactic body radiotherapy. Methods: Thirty-five men with low- and intermediate-risk prostate cancer who underwent rectal hydrogel spacer placement and pre-, post-spacer prostate MRI studies were treated with prostate SBRT (36.25 Gy in five fractions). A prostate radiologist contoured the NVB on both the pre- and post-spacer T2W MRI sequences that were then registered to the CT simulation scan for NVB-sparing radiation treatment planning. Three SBRT treatment plans were developed for each patient: (1) no NVB sparing, (2) NVB-sparing using pre-spacer MRI, and (3) NVB-sparing using post-spacer MRI. NVB dose constraints include maximum dose 36.25 Gy (100%), V34.4 Gy (95% of dose) <60%, V32Gy <70%, V28Gy <90%. Results: Rectal hydrogel spacer placement shifted NVB contours an average of 3.1 ± 3.4 mm away from the prostate, resulting in a 10% decrease in NVB V34.4 Gy in non-NVB-sparing plans (p < 0.01). NVB-sparing treatment planning reduced the NVB V34.4 by 16% without the spacer (p < 0.01) and 25% with spacer (p < 0.001). NVB-sparing did not compromise PTV coverage and OAR endpoints. Conclusions: NVB-sparing SBRT with rectal hydrogel spacer significantly reduces the volume of NVB treated with high-dose radiation. Rectal spacer contributes to this effect through a dosimetrically meaningful displacement of the NVB that may significantly reduce RiED. These results suggest that NVB-sparing SBRT warrants further clinical evaluation. Advances in knowledge: This is a feasibility study showing that the periprostatic NVBs can be spared high doses of radiation during prostate SBRT using a hydrogel spacer and nerve-sparing treatment planning.

Better preservation of erectile function in localized prostate cancer patients with modern proton therapy: Is it cost‐effective?

“…Lastly, at the current stage, the benefits of protons in sexual function preservation have not yet been fully explored. In recent years, a functional anatomy‐based approach, i.e., the use of prespecified dose constraints for critical erectile structures such as penile bulb, corpus cavernosum, and internal pudendal artery, has been recommended for prostate irradiation to maximize erectile function preservation 37–39 . The relevant studies are currently based on photon modalities.…”

“…In recent years, a functional anatomy-based approach, i.e., the use of prespecified dose constraints for critical erectile structures such as penile bulb, corpus cavernosum, and internal pudendal artery, has been recommended for prostate irradiation to maximize erectile function preservation. [37][38][39] The relevant studies are currently based on photon modalities. Theoretically, functional structure sparing could be more achievable by using the PBS protons.…”

Technologies to reduce radiation toxicity in prostate cancer patients: spacers - a simple and effective solution

“…Переменные, характеризующие величину дозной нагрузки на СНП, в группах имели следующие значения: D mean (средняя доза) -7,72 и 9,07 Гр (p <0,05), V 75 % (доза, подводимая к 75 % объема СНП) -12,1 и 26,8 % (p <0,05) соответственно. Представляет несомненный интерес недавнее исследование M. E. Hwang и соавт., в котором было показано, что введение спейсера вызывает смещение СНП от капсулы железы в среднем на 3,1 ± 3,4 мм [53] (см. рис.…”

Longitudinal Changes in U.S. Parameters of Neurovascular Bundles Suggest Mechanism for Radiation-Induced Erectile Dysfunction

“… 4 Recent investigations focus on the neurovascular bundles (NVB). 5 NVB-sparing radiation therapy has been demonstrated to be feasible in terms of contour reproducibility 6 and radiation therapy planning, 7 including in the presence of SpaceOAR 8 or with boost to dominant intraprostatic lesion. 9 However, functional assessments of NVB before and after radiation have not been reported.…”