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

Document Type: Original Paper

Authors

1 Department of Radiation Oncology, Dr.RMLIMS, Lucknow, India

2 Department of Radiation Oncology, Dr.RMLIMS, Lucknow, India.

3 Department of Radiation Oncology, Dr. Ram Manohar Lohia Institute of Medical Sciences, Vibhuti Khand Gomti Nagar, Lucknow -226010 India

4 Department of Radiation Oncology, Dr. Ram Manohar Lohia Institute of Medical Sciences, Vibhuti Khand Gomti Nagar, Lucknow -226010

5 Department of Pathology, Dr.RMLIMS, Lucknow, India.

6 Head, Department of Radiation Oncology, Dr.RMLIMS, Lucknow

Abstract

Introduction: 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).
Material and Methods: 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.
Results: 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.
Conclusion: VMAT achieved better coverage of the PTV and delivered fewer doses to bilateral optic nerve and chiasm.

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Volume 16, Issue 5
September and October 2019
Pages 385-391
  • Receive Date: 14 November 2018
  • Revise Date: 19 February 2019
  • Accept Date: 03 March 2019