# Assessment and Comparison of 3D Conformal Radiotherapy With Volumetric Modulated Arc Therapy for Preserving Remaining Brain Volume in High-Grade Gliomas

## TL;DR

This study compares two radiotherapy techniques for brain tumors, finding that VMAT provides better dose conformity but affects brain volume differently at low and high doses.

## Contribution

The study provides a novel dosimetric comparison of VMAT and 3D-CRT focusing on remaining brain volume in high-grade glioma patients.

## Key findings

- VMAT showed superior dose conformity compared to 3D-CRT (p-value 0.001).
- 3D-CRT favored low-to-medium dose volumes in remaining brain volume, while VMAT favored medium-to-high dose volumes.
- Whole brain mean dose was not significantly different between the two techniques.

## Abstract

Introduction

Tri-modality therapy, consisting of maximal safe resection, concurrent chemo-radiation, and adjuvant chemotherapy, is the standard approach for the treatment of high-grade glioma (HGGs). Intensity modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) have excellent potential to reduce the doses to organs at risk (OARs) with optimal dose conformity. However, the literature on the dosimetric parameters for remaining brain volume (RBV) and its relative comparison is limited.

Methods

We conducted a retrospective study for which the inclusion criteria were being over the age of 18 years and having a histologically proven post-operative HGG with a Karnofsky performance score (KPS) >60. The prescription dose was similar in both techniques (60 Gray in 30 fractions at 2 Gray per fraction). The primary objective was to evaluate and compare the dosimetric profiles of V5, V10, V20, V30, V40, V50, and V60 of the RBV. The secondary objective was to document and compare the doses received by OARs in three-dimensional conformal radiotherapy (3D-CRT) and VMAT.

Results

The planning data of 24 patients were analyzed. The demographic profile was age (<40, 42%; > 40, 58%), male (58%) and female (42%), KPS (60, 12%; 70, 54%; 80, 33%), histopathological grade III (30%) and IV (70%), and tumor location (frontal 50%, parietal 21%, temporal 17%, and occipital 12%). In 79% of the patients, the tumor crossed midline. The VMAT plan showed superior dose conformity compared with the 3D-CRT plan (p-value 0.001). The low-to-medium dose volumes (V5, V10, V20, and V30) of the RBV were found to be statistically significant, thus favoring the 3D-CRT plan, but the medium-to-high dose volumes (V50 and V60), which were high in the 3D-CRT plan, favored the VMAT plan. However, the whole brain mean dose did not show any significant difference.

Conclusion

The VMAT plan showed superior dose conformity compared with the 3D-CRT plan. However, the RBV among the patients receiving the low doses was greater in the VMAT plan than in the 3D-CRT plan, while the RBV among those receiving high doses was significantly greater in the 3D-CRT plan.