Differding Sarah, Sterpin Edmond, Hermand Nicolas, Vanstraelen Bianca, Nuyts Sandra, de Patoul Nathalie, Denis Jean-Marc, Lee John Aldo, Grégoire Vincent
Department of Radiation Oncology, and Center for Molecular Imaging, Oncology and Radiotherapy (MIRO), Université catholique de Louvain, Institut de Recherche Expérimentale et Clinique (IREC), Brussels, Belgium.
Department of Oncology, Experimental Radiation Oncology, KU Leuven - University of Leuven, Leuven, Belgium.
Radiat Oncol. 2017 Mar 23;12(1):59. doi: 10.1186/s13014-017-0793-0.
Validation of dose escalation through FDG-PET dose painting (DP) for oropharyngeal squamous cell carcinoma (SCC) requires randomized clinical trials with large sample size, potentially involving different treatment planning and delivery systems. As a first step of a joint clinical study of DP, a planning comparison was performed between Tomotherapy HiArt® (HT) and Varian RapidArc® (RA).
The planning study was conducted on five patients with oropharyngeal SCC. Elective and therapeutic CTVs were delineated based on anatomic information, and the respective PTVs (CTVs + 4 mm) were prescribed a dose of 56 (PTV) and 70 Gy (PTV). A gradient-based method was used to delineate automatically the external contours of the FDG-PET volume (GTV). Variation of the FDG uptake within the GTV was linearly converted into a prescription between 70 and 86 Gy. A dilation of the voxel-by-voxel prescription of 2.5 mm was applied to account for geometric errors in dose delivery (PTV). The study was divided in two planning phases aiming at maximizing target coverage (phase I) and lowering doses to OAR (phase II). A Quality-Volume Histogram (QVH) assessed conformity with the DP prescription inside the PTV.
In phase I, for both HT and RA, all plans achieved comparable target coverage for PTV and PTV, respecting the planning objectives. A median value of 99.9 and 97.2% of all voxels in the PTV received at least 95% of the prescribed dose for RA and HT, respectively. A median value of 0.0% and 3.7% of the voxels in the PTV received 105% or more of prescribed dose for RA and HT, respectively. In phase II, no significant differences were found in OAR sparing. Median treatment times were 13.7 min for HT and 5 min for RA.
Both HT and RA can generate similar dose distributions for FDG-PET based dose escalation and dose painting in oropharyngeal SCC patients.
通过氟代脱氧葡萄糖正电子发射断层扫描（FDG-PET）剂量描绘（DP）对口咽鳞状细胞癌（SCC）进行剂量递增验证需要进行大样本量的随机临床试验，可能涉及不同的治疗计划和输送系统。作为DP联合临床研究的第一步，在螺旋断层放射治疗系统（Tomotherapy HiArt®，HT）和瓦里安容积调强弧形治疗系统（Varian RapidArc®，RA）之间进行了计划比较。
对5例口咽SCC患者进行计划研究。根据解剖信息勾勒出选择性和治疗性临床靶区（CTV），并对相应的计划靶区（PTV，CTV + 4 mm）分别给予56（PTV）和70 Gy（PTV）的剂量。使用基于梯度的方法自动勾勒出FDG-PET体积（GTV）的外部轮廓。GTV内FDG摄取的变化被线性转换为70至86 Gy之间的处方剂量。对逐体素处方进行2.5 mm的扩张，以考虑剂量输送（PTV）中的几何误差。该研究分为两个计划阶段，旨在最大化靶区覆盖（阶段I）和降低危及器官（OAR）的剂量（阶段II）。质量-体积直方图（QVH）评估PTV内与DP处方的符合程度。
在阶段I，对于HT和RA，所有计划在实现PTV和PTV的靶区覆盖方面相当，均符合计划目标。RA和HT的PTV中分别有99.9%和97.2%的体素接受了至少95%的处方剂量。RA和HT的PTV中分别有0.0%和3.7%的体素接受了105%或更多的处方剂量。在阶段II，在OAR保护方面未发现显著差异。HT的中位治疗时间为13 .分钟，RA为5分钟。
HT和RA在口咽SCC患者基于FDG-PET的剂量递增和剂量描绘中均可产生相似的剂量分布。
