Cheung Eva Y W, Ng Shirley S H, Yung Sapphire H Y, Cheng Dominic Y T, Chan Fandy Y C, Cheng Janice K Y
School of Medical Health and Sciences, Tung Wah College, 19/F, 31 Wylie Road, Ho Man Tin, Hong Kong, China.
Department of Clinical Oncology, Queen Mary Hospital, Pok Fu Lam, Hong Kong, China.
Life (Basel). 2022 Jan 28;12(2):195. doi: 10.3390/life12020195.
This study aimed to identify the better arc configuration of volumetric modulated arc therapy (VMAT) for high-grade glioma and glioblastoma, focusing on a dose reduction to the hypothalamic-pituitary axis through an analysis of dose-volumetric parameters, as well as a correlation analysis between the planned target volume (PTV) to organs at risk (OAR) distance and the radiation dose.
Twenty-four patients with 9 high-grade glioma and 15 glioblastomas were included in this study. Identical CT, MRI and structure sets of each patient were used for coplanar VMAT (CO-VMAT), dual planar VMAT (DP-VMAT) and multi-planar VMAT (MP-VMAT) planning. The dose constraints adhered to the RTOG0825 and RTOG9006 protocols. The dose-volumetric parameters of each plan were collected for statistical analysis. Correlation analyses were performed between radiation dose and PTV-OARs distance.
The DP-VMAT and MP-VMAT achieved a significant dose reduction to most nearby OARs when compared to CO-VMAT, without compromising the dose to PTV, plan homogeneity and conformity. For centrally located OARs, including the hypothalamus, pituitary, brain stem and optic chiasm, the dose reductions ranged from 2.65 Gy to 3.91 Gy ( < 0.001) in DP-VMAT and from 2.57 Gy to 4 Gy ( < 0.001) in MP-VMAT. Similar dose reduction effects were achieved for contralaterally located OARs, including the hippocampus, optic nerve, lens and retina, ranging from 1.06 Gy to 4.37 Gy in DP-VMAT and from 0.54 Gy to 3.39 Gy in MP-VMAT. For ipsilaterally located OARs, DP-VMAT achieved a significant dose reduction of 1.75 Gy to D for the optic nerve. In the correlation analysis, DP-VMAT and MP-VMAT showed significant dose reductions to centrally located OARs when the PTV-OAR distance was less than 4 cm. In particular, DP-VMAT offered better sparing to the optic chiasm when it was located less than 2 cm from the PTV than that of MP-VMAT and CO-VMAT. DP-VMAT and MP-VMAT also showed better sparing to the contralateral hippocampus and retina when they were located 3-8 cm from the PTV.
The proposed DP-VMAT and MP-VMAT demonstrated significant dose reductions to centrally located and contralateral OARs and maintained the high plan qualities to PTV with good homogeneity and conformity when compared to CO-VMAT for high-grade glioma and glioblastoma. The benefit in choosing DP-VMAT and MP-VMAT over CO-VMAT was substantial when the PTV was located near the hypothalamus, pituitary, optic chiasm, contralateral hippocampus and contralateral retina.
本研究旨在确定容积调强弧形放疗（VMAT）用于高级别胶质瘤和胶质母细胞瘤时的更佳弧形配置，通过分析剂量 - 体积参数以及计划靶区（PTV）与危及器官（OAR）距离和辐射剂量之间的相关性分析，重点是降低下丘脑 - 垂体轴的剂量。
本研究纳入了24例患者，其中9例为高级别胶质瘤，15例为胶质母细胞瘤。使用每位患者相同的CT、MRI和结构集进行共面VMAT（CO - VMAT）、双平面VMAT（DP - VMAT）和多平面VMAT（MP - VMAT）计划。剂量限制遵循RTOG0825和RTOG9006方案。收集每个计划的剂量 - 体积参数进行统计分析。对辐射剂量与PTV - OARs距离进行相关性分析。
与CO - VMAT相比，DP - VMAT和MP - VMAT在不影响PTV剂量、计划均匀性和适形性的情况下，使大多数附近OARs的剂量显著降低。对于位于中心的OARs，包括下丘脑、垂体、脑干和视交叉，DP - VMAT的剂量降低范围为2.65 Gy至3.91 Gy（<0.001），MP - VMAT的剂量降低范围为2.57 Gy至4 Gy（<0.001）。对于对侧的OARs，包括海马体、视神经、晶状体和视网膜，也实现了类似的剂量降低效果，DP - VMAT的剂量降低范围为1.06 Gy至4.37 Gy，MP - VMAT的剂量降低范围为0.54 Gy至3.39 Gy。对于同侧的OARs，DP - VMAT使视神经的D剂量显著降低1.75 Gy。在相关性分析中，当PTV - OAR距离小于4 cm时，DP - VMAT和MP - VMAT对位于中心的OARs显示出显著的剂量降低。特别是，当视交叉距离PTV小于2 cm时, DP - VMAT对视交叉的保护比MP - VMAT和CO - VMAT更好。当对侧海马体和视网膜距离PTV为3 - 8 cm时，DP - VMAT和MP - VMAT对它们也显示出更好的保护。
与CO - VMAT相比，所提出的DP - VMAT和MP - VMAT在高级别胶质瘤和胶质母细胞瘤中，对位于中心和对侧的OARs显示出显著的剂量降低，并保持了对PTV的高计划质量，具有良好的均匀性和适形性。当PTV位于下丘脑、垂体、视交叉、对侧海马体和对侧视网膜附近时，选择DP - VMAT和MP - VMAT优于CO - VMAT的益处显著。
