# A Dosimetric Comparison of Coplanar Versus Noncoplanar Volumetric Modulated Arc Therapy (VMAT) for High Grade Glioma

## TL;DR

This study compares two radiotherapy techniques for high-grade gliomas and finds that noncoplanar VMAT offers better protection for certain sensitive organs.

## Contribution

The study provides a direct dosimetric comparison of cVMAT and NcVMAT for high-grade glioma treatment.

## Key findings

- Both cVMAT and NcVMAT showed similar PTV doses and conformity/heterogeneity indices.
- NcVMAT reduced maximum doses to the optic chiasma and cochlea significantly.
- NcVMAT plans had equal monitor units per fraction compared to cVMAT.

## Abstract

Objective: This study aims to compare the dosimetric differences in radiotherapy plans generated by coplanar volumetric-modulated arc therapy (cVMAT) and noncoplanar volumetric-modulated arc therapy (NcVMAT) for high-grade gliomas.

Material and methods: This is a single-institutional, prospective, observational study conducted during a period of one year from December 2018 to October 2019. A total of 15 consecutive patients with high-grade gliomas who planned to receive postoperative radiotherapy were included in the study. Plans were generated using both cVMAT and NcVMAT for each patient. The plans were evaluated per the International Commission on Radiation Units and Measurements (ICRU) Report 83 criteria. A dosimetric comparison of each plan was made in terms of target coverage and dose to organs at risk (OARs).

Results: On analyzing the results, the two techniques resulted in comparable maximum, mean, and minimum planning target volume (PTV) doses. There were statistically insignificant numerical differences observed in the conformity index (CI) and heterogeneity index (HI). Maximum optic chiasma and ipsilateral cochlea doses were statistically lower in the NcVMAT plan compared to the cVMAT plan (p-value = 0.002). The NcVMAT plans had insignificant differences in monitor units (MU) per fraction.

Conclusion: This study highlights equal PTV coverage, homogeneity, and conformity indices between cVMAT and NcVMAT plans. A better dosimetric profile of the optic chiasma, cochlea, and equal MU per fraction favors the NcVMAT technique for treating high-grade gliomas.