Amaloo Christopher, Nazareth Daryl P, Kumaraswamy Lalith K
Department of Radiation Medicine, Roswell Park Cancer Institute, Buffalo, NY, USA.
Department of Radiation Medicine, Roswell Park Cancer Institute and Department of Biophysics and Physiology, University at Buffalo, Buffalo, USA.
Radiol Oncol. 2015 Aug 21;49(3):291-8. doi: 10.1515/raon-2015-0018. eCollection 2015 Sep.
Volumetric modulated arc therapy (VMAT) has quickly become accepted as standard of care for the treatment of prostate cancer based on studies showing it is able to provide faster delivery with adequate target coverage and reduced monitor units while maintaining organ at risk (OAR) sparing. This study aims to demonstrate the potential to increase dose conformality with increased planner control and OAR sparing using a hybrid treatment technique compared to VMAT.
Eleven patients having been previously treated for prostate cancer with VMAT techniques were replanned with a hybrid technique on Varian Treatment Planning System. Multiple static IMRT fields (2 to 3) were planned initially based on critical OAR to reduce dose but provide some planning treatment volume (PTV) coverage. This was used as a base dose plan to provide 30-35% coverage for a single arc VMAT plan.
The clinical VMAT plan was used as a control for the purposes of comparison. Average of all OAR sparing between the hybrid technique and VMAT showed the hybrid plan delivering less dose in almost all cases except for V80 of the bladder and maximum dose to right femoral head. PTV coverage was superior with the VMAT technique. Monitor unit differences varied, with the hybrid plan able to deliver fewer units 37% of the time, similar results 18% of the time, and higher units 45% of the time. On average, the hybrid plan delivered 10% more monitor units.
The hybrid plan can be delivered in a single gantry rotation combining aspects of VMAT with regions of dynamic intensity modulated radiation therapy (IMRT) within the treatment arc.
容积调强弧形放疗（VMAT）已迅速被接受为前列腺癌治疗的护理标准，基于多项研究表明它能够在保持危及器官（OAR）受量较低的同时，更快地完成照射，实现足够的靶区覆盖并减少监测单位（MU）。本研究旨在证明，与VMAT相比，使用混合治疗技术通过增加计划者的控制和减少OAR受量来提高剂量适形性的潜力。
对11例先前用VMAT技术治疗过前列腺癌的患者，在瓦里安治疗计划系统上用混合技术重新进行计划。最初根据关键OAR计划多个静态调强放疗野（2至3个），以降低剂量，但提供一定的计划治疗体积（PTV）覆盖。这被用作基础剂量计划，为单弧VMAT计划提供30%-35%的覆盖。
将临床VMAT计划用作对照进行比较。混合技术与VMAT之间所有OAR受量的平均值显示，除膀胱V80和右股骨头最大剂量外，混合计划在几乎所有情况下的受量都更低。VMAT技术的PTV覆盖更好。监测单位差异各不相同，混合计划在37%的时间内能够减少MU，在18%的时间内结果相似，在45%的时间内MU更高。平均而言，混合计划的监测单位多10%。
混合计划可在单个机架旋转中完成，将VMAT的各方面与治疗弧内的动态调强放疗（IMRT）区域相结合。
