Comparison of Volumetric Modulated Arc Therapy and Three-Dimensional Conformal Radiotherapy in Postoperative High-Grade Glioma: A Dosimetric Comparison

We aimed to dosimetrically compare three-dimensional conformal radiotherapy (3D-CRT) and volumetric modulated arc therapy (VMAT) in terms of planning target volume (PTV) coverage, organ at risk (OAR) sparing, and conformity index (CI).

Planning data of 26 high grade glioma (HGG) patients were used. Prescribed dose for 3D-CRT was 46Gy in 23 fractions to low-risk PTV (LR-PTV) and 14 Gy in 7 fractions to high-risk PTV (HR-PTV). VMAT plans were conducted using 46 Gy in 30 fractions to LR-PTV and 60 Gy in 30 fractions to HR-PTV.

Tumor locations were frontal, parietal, temporal, and multi-lobed in 27%, 15%, 23%, and 35% of cases, respectively. Histology was glioblastoma multiform in 89% of patients. Mean values of PTV D95 (dose received by 95% volume) in 3D-CRT and VMAT were 96.6% and 98.8% for the LR-PTV and 97.3% and 99% for HR-PTV (P<0.001), respectively. Mean values of CI in 3D-CRT were 0.96 and 0.97 for LR-PTV and HR-PTV and 0.98 and 0.99 for LR-PTV and HR-PTV of VMAT (both P<0.001), respectively. Mean Dmax of right optic nerve (maximum point dose received by the organ) for 3D-CRT and VMAT were 31.59 and 25.57Gy (P=0.02). Mean Dmax for left optic nerve and optic chiasm were 28.81 and 22.14 Gy (P=0.019) and 42.24 and 37.12 Gy (P=0.055) respectively for 3D-CRT versus VMAT. Doses to other OARs were not statistically different between 3D-CRT and VMAT.

VMAT achieved better coverage of the PTV and delivered fewer doses to bilateral optic nerve and chiasm.