A Randomized Trial of Comparative Dosimetric Study of Radiotherapy in High Grade Gliomas Based on the Guidelines of 2019-NRG and EORTC Target Delineation

Abstract

<h3>Purpose/Objective(s)</h3> Postoperative radiotherapy is important for high-grade glioma (WHO Grade 3-4), but the optimal way for contouring the target area for radiotherapy is still unclear. The purpose of this randomized trial was to compare the dosimetric differences in radiation treatment plans (TPS) generated based on the European Organization for Research and Treatment of Cancer (EORTC) and NRG consensus (NRG-2019) guidelines to provide evidence for optimal target delineation for high-grade glioma. <h3>Materials/Methods</h3> Patients with diagnosis of high-grade glioma were randomly assigned (1:1) to receive postoperative radiotherapy based on either EORTC guideline or NRG-2019 guideline. We report the result of dosimetric comparison first. In 13 high grade glioma patients, both EORTC and NRG-2019 radiation treatment plans were generated for dosimetric comparison. For EORTC group, the prescription dose was 95% PTV 60 Gy in 30 fractions. The gross tumor volume (GTV) including resection cavity and residual tumor encompassed the T1-weighted images (T1WI) and T2 FLAIR contrast-enhancing lesion. For NRG-2019group, GTV involved the T1-weighted images (T1WI) and T2 FLAIR contrast-enhancing foci and peritumoral edema on the preoperative CT or MRI. The prescription dose of PTV1 was 46 Gy in 23 fractions. The areas were then diminished to contain merely the contrast enhancing foci with a 2.5 cm margin as CTV2, and PTV2 was equal the CTV2 plus 0.3 cm margin for additional prescription dose was 14 Gy in 7 fractions. It should be noted that CTV1 and CTV2 were trimmed according to the anatomical barriers, falx, ventricles, etc. This trial is registered with chictr.org.cn, number ChiCTR2100046667. <h3>Results</h3> The median volume for PTV of EORTC plans, PTV1 of NRG-2019 plans, PTV2 of NRG-2019 plans were 336.6 cm³ (range 161.1-511.5 cm³), 365.3 cm³ (range 123.4-535.0 cm³), and 263.2 cm³ (range 116.8-497.7 cm³), respectively. Both treatment plans were found to have similar efficiency and evaluated as acceptable for patient treatment. Both treatment plans showed well conformal index and homogeneity index and were not statistically significantly different. There was no significant difference in the volume percent of brain irradiated to 30 Gy, 46 Gy, and 60 Gy according to different target delineations (P = 0.397, P = 0.590 and P = 0.739, respectively). These two plans also showed no significant differences in the doses to the brainstem, optic chiasm, optic nerve, lens, eyes, pituitary, and temporal lobes (P = 0.858, P = 0.858, 0.701, P = 0.794, P = 0.701, P = 0.427, P = 0.489, P = 0.898, P = 0.626, P = 0.942 and P = 0.161, respectively). <h3>Conclusion</h3> Compared with EORTC guidelines for postoperative radiotherapy for high-grade glioma, the NRG-2019 target area delineation guidelines were able to include peritumor edema in the CTV without increasing the radiation dose to organs at risk (OARs). This study further provides a foundation for the application of the NRG-2019 consensus in radiotherapy for patients with high-grade gliomas.