Prog Med Phys.  2019 Mar;30(1):7-13. 10.14316/pmp.2019.30.1.7.

Comparison of Dosimetrical and Radiobiological Parameters on Three VMAT Techniques for Left-Sided Breast Cancer

• Kang SH
• Chung JB
• Kim KH
• Kang SW
• Eom KY
• Song C
• Kim IA
• Kim JS

• KMID: 2442416
• DOI: http://doi.org/10.14316/pmp.2019.30.1.7

Abstract

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 Eclipseâ„¢ 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 VitalBEAMâ„¢. The same dose objectives for each plan were used to achieve a fair comparison during optimization.
RESULTS
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.
CONCLUSIONS
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.

Keyword

Left sided breast cancer; Volumetric modulated arc therapy; Dosimetrical parameters; Radiobiological parameters

MeSH Terms

Breast Neoplasms
Humans
Lung
Organs at Risk
Radiotherapy, Intensity-Modulated
Retrospective Studies
Unilateral Breast Neoplasms*

Figure

• 

  Fig. 1 Example of dose distribution in transverse plane for (a) 1pVMAT, (b) 2pVMAT, and (c) 2tVMAT.

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