Chi Mei Medical Center Yungkang City 701 44, Tainan County
W. J. Hong, H. M. Lin, C. J. Tsai, C. C. Yang, and H. W. Ho; Department of Radiation Oncology, Chi Mei Medical Center, Tainan, Taiwan
Purpose/Objective(s): Minimizing radiation dose to normal tissues to preserve neurological function is a critical concern for glioblastoma (GBM) patients undergoing radiotherapy. This study aimed to compare the dosimetric quality and impact on adjacent organs at risk (OARs) between HyperArc (HA), volumetric arc therapy (VMAT), and non-coplanar VMAT (NC-VMAT) plans. Materials/
Methods: Twenty-seven GBM patients who received intensity-modulated radiotherapy or VMAT from 2012 to 2022 at our institution were enrolled. Replans were generated for each patient using HA, VMAT, and NC-VMAT techniques, maintaining the same patient-specific target dose prescription and OAR constraints. The prescribed doses included 46 Gy in 23 fractions to the planning target volume (PTV46), followed by a boost to PTV60 with 14 Gy in 7 fractions, resulting in a total cumulative dose of 60 Gy. Dosages to target volumes (GTV and PTV60) and OARs (brain, brainstem, optic nerves, eyes, and chiasma) were compared using statistical analyses. Additionally, target coverage and dosimetric parameters such as conformity index (CI), homogeneity index (HI), high dose spillage, and gradient radius were also evaluated. Results: The GTV coverage for HyperArc (HA), VMAT, and NC-VMAT plans was 99.54%, 98.94%, and 99.38%, respectively. Correspondingly, the PTV60 coverage for HA, VMAT, and NC-VMAT plans was 97.27%, 96.34%, and 97.07%. Notably, HA plans exhibited significantly superior coverage compared to VMAT and NC-VMAT plans (p<0.05). The HA technique also demonstrated a greater reduction in doses to the brain, brainstem, chiasm, optic nerve, and lens while maintaining target coverage, compared to VMAT and NC-VMAT plans (p<0.05). Furthermore, HA plans showed superior dosimetric quality, including improved CI (1.14 vs.1.23 vs. 0.98), reduced high dose spillage at 46 Gy (0.17 vs. 0.34 vs. 0.33), decreased intermediate dose spillage at 60 Gy (3.42 vs. 4.45 vs. 2.07) and 46 Gy (2.15 vs. 2.77 vs. 2.59), and a smaller gradient radius at 60 Gy (1.61 cm vs. 2.03 cm vs. 1.90 cm) and 46 Gy (0.94 cm vs. 1.27 cm vs. 1.14 cm), compared to VMAT and NC-VMAT plans. Conclusion: In the treatment of GBM patients, HA plans outperformed VMAT and NC-VMAT by providing excellent target coverage, superior sparing of normal tissues, and enhanced dosimetric quality. These findings suggest that HA may contribute to improved treatment efficacy for GBM patients undergoing radiotherapy.
