Original Research

A dosimetric comparison of volumetric modulated arc therapy with three-dimensional conformal radiotherapy in the treatment of cervical cancer

Visham Bhagaloo, Nazreen Bhim, Alistair Hunter, Nazia Fakie
South African Journal of Oncology | Vol 5 | a149 | DOI: https://doi.org/10.4102/sajo.v5i0.149 | © 2021 Visham Bhagaloo, Nazreen Bhim, Alistair Hunter, Nazia Fakie | This work is licensed under CC Attribution 4.0
Submitted: 05 August 2020 | Published: 22 January 2021

About the author(s)

Visham Bhagaloo, Division of Radiation Medicine, Faculty of Health Sciences, Groote Schuur Hospital, University of Cape Town, Cape Town, South Africa
Nazreen Bhim, Division of Radiation Medicine, Faculty of Health Sciences, Groote Schuur Hospital, University of Cape Town, Cape Town, South Africa
Alistair Hunter, Division of Radiation Medicine, Faculty of Health Sciences, Groote Schuur Hospital, University of Cape Town, Cape Town, South Africa
Nazia Fakie, Division of Radiation Medicine, Faculty of Health Sciences, Groote Schuur Hospital, University of Cape Town, Cape Town, South Africa


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Abstract

Background: External beam radiotherapy (EBRT) is essential in the management of locally advanced cervical cancer (LACC). Volumetric modulated arc therapy (VMAT) is thought to achieve higher conformity to the planned target volume (PTV) and better sparing of organs at risk (OAR) when compared to three-dimensional conformal radiotherapy (3D-CRT). This study focused on these principles as it applied to treatment and potential toxicity in the management of LACC.

Aim: The aim of this study was to compare dosimetric parameters between VMAT and 3D-CRT in the management of LACC.

Setting: The study analysed patients treated at Groote Schuur Hospital (GSH) between May and December 2017.

Methods: This is a non-randomised comparative retrospective study. Three-dimensional conformal radiation and VMAT plans were generated, and data on treatment parameters for PTV D50%, Dmax, Dmean, conformity index (CI), homogeneity index (HI), treated volume (TV), irradiated volume (IV) and OAR constraints; femoral heads, bladder, bowel bag, rectum and bone marrow were collected.

Results: Of the 45 patients assessed, VMAT showed statistically significant, lower treatment parameter values for CI (1.09 vs. 1.49) and TV (1613.1 cm3 vs. 2230.3 cm3), whereas 3D-CRT showed lower Dmax (48.1 Gy vs. 49.2 Gy) and IV (10652.2 cm3 vs. 14618.1 cm3). Volumetric modulated arc therapy OAR doses revealed a lower V45 for bowel bag (182.3 cm3 vs. 411.3 cm3; p < 0.001), lower V40 for bone marrow (19.1% vs. 38.7%; p < 0.001) and rectum (88.5% vs. 96%; p < 0.001). A reduced 3D-CRT dose was noted for bladder Dmax (47.4 Gy vs. 48.3 Gy; p < 0.001).

Conclusion: Volumetric modulated arc therapy offered a superior dosimetric option, with better OAR dose sparing and optimal tumour dosimetry.


Keywords

cervical cancer; VMAT; 3D-CRT; radiation therapy; dosimetry

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