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Comparison of Dosimetrical and Radiobiological Parameters on Three VMAT Techniques for Left-Sided Breast Cancer
Prog. Med. Phys. 2019;30(1):7-13
Published online March 31, 2019
© 2019 Korean Society of Medical Physics.

Seong-Hee Kang1, Jin-Beom Chung1, Kyung-Hyeon Kim2, Sang-Won Kang2, Keun-Yong Eom1, Changhoon Song1, In-Ah Kim1, Jae-Sung Kim1

1Department of Radiation Oncology, Seoul National University Bungdang Hospital, Seongnam, 2Department of Biomedicine and Health
Sciences, Research Institute of Biomedical Engineering, College of Medicine, The Catholic University of Korea, Seoul, Korea
Correspondence to: Jin-Beom Chung, (
Tel: 82-31-787-7654, Fax: 82-31-787-4019
Received December 12, 2018; Revised December 27, 2018; Accepted January 17, 2019.
This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Purpose: To compare the dosimetrical and radiobiological parameters among various volumetric modulated arc therapy (VMAT) techniques using restricted and continuous arc beams for left-sided breast cancer.

Materials and Methods:
Ten patients with left-sided breast cancer without regional nodes were retrospectively selected and prescribed the dose of 42.6 Gy in 16 fractions on the planning target volume (PTV). For each patient, three plans were generated using the EclipseTM system (Varian Medical System, Palo Alto, CA) with one partial arc 1pVMAT, two partial arcs 2pVMAT, and two tangential arcs 2tVMAT. All plans were calculated through anisotropic analytic algorithm and photon optimizer with 6 MV photon beam of VitalBEAMTM. The same dose objectives for each plan were used to achieve a fair comparison during optimization.

For PTV, dosimetrical parameters such as Homogeneity index, conformity index, and conformal number were superior in 2pVMAT than those in both techniques. V95%, which indicates PTV coverage, was 91.86%, 96.60%, and 96.65% for 1pVMAT, 2pVMAT, and 2tVMAT, respectively. In most organs at risk (OARs), 2pVMAT significantly reduced the delivered doses compared with the other techniques, excluding the doses to contralateral lung. For the analysis of radiobiological parameters, a significant difference in normal tissue complication probability was observed in ipsilateral lung while no difference was observed in the other OARs.

Our study showed that 2pVMAT had better plan quality and normal tissue sparing than 1pVMAT and 2tVMAT but not for all parameters. Therefore, 2pVMAT could be considered the priority choice for the treatment planning for left breast cancer.
Keywords : Left sided breast cancer, Volumetric modulated arc therapy, Dosimetrical parameters, Radiobiological parameters

March 2019, 30 (1)