Abstract
PurposeThis study aims to evaluate the best possible practice using hybrid volumetric modulated arc therapy (H-VMAT) for hypofractionated radiation therapy of breast cancer. Different combinations of H‑VMAT—a combination of three-dimensional radiotherapy (3D-CRT) and VMAT—were analyzed regarding planning target volume (PTV), dose coverage, and exposure to organs at risk (OAR).MethodsPlanning computed tomography scans were acquired in deep-inspiration breath-hold. A total of 520 treatment plans were calculated and evaluated for 40 patients, comprising six different H‑VMAT plans and a 3D-CRT plan as reference. H‑VMAT plans consisted of two treatment plans including 3D-CRT and VMAT. During H‑VMAT planning, the use of hard wedge filters (HWF) and beam energies were varied. The reference plans were planned with mixed beam energies and the inclusion/omission of HWF.ResultsCompared to the reference treatment plans, all H‑VMAT plans showed consistently better PTV dose coverage, conformity, and homogeneity. Additionally, OAR protection was significantly improved with several H‑VMAT combinations (p < 0.05). The comparison of different H‑VMAT combinations showed that inclusion of HWF in the base plan had a negative impact on PTV dose coverage, conformity, and OAR exposure. It also increased the planned monitor units and beam-on time. Advantages of using lower beam energies (6-MV photons) in both the base plan and in the VMAT supplementary dose were observed.ConclusionThe H‑VMAT technique is an effective possibility for generating homogenous and conformal dose distributions. With the right choice of H‑VMAT combination, superior OAR protection is achieved compared to 3D-CRT.
Highlights
Radiotherapy (RT) is pivotal in the adjuvant treatment of breast cancer, improving both local control and overall survival [1, 2]
We examined the impact of different variations with respect to hard wedge filters (HWF) in the 3D-CRT base plan and beam energies for the application of hybrid volumetric arc therapy (H-volumetric modulated arc therapy (VMAT))
H-VMAT hybrid volumetric modulated arc therapy, HV1–HV6 H-VMAT constellations, Ref reference treatment plan, COV planning target volume dose coverage, EI external index, CN conformation number, homogeneity within the PTV (HI) homogeneity index, ipsilateral lung (IL) ipsilateral, CB contralateral, VX volume (%) of the organ at risk (OAR) exposed to at least X Gy, D5 minimal dose (Gy) in 5% of the organs at risk (OAR) volume with the highest exposure, Dmean mean dose aHV1–HV6 are presented with p-values to demonstrate significant differences to Ref, using a two-sided Wilcoxon rank sum test for paired samples for the statistical analysis cantly better values for PTV dose coverage (Fig. 1, Table 3)
Summary
Radiotherapy (RT) is pivotal in the adjuvant treatment of breast cancer, improving both local control and overall survival [1, 2]. Various radiation concepts and techniques have been established over time. Static three-dimensional radiotherapy (3D-CRT) represents the conventional radiation technique, whereby tangential opposing fields with hard wedge filters (HWF) are used. Modern dynamic irradiation techniques, such as intensity-modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT), attempt to generate more homogeneous and conformal dose distributions for the planning target volume (PTV). Better protection of organs at risk (OAR) may be achieved [3, 4]. Dynamic radiation techniques bear the risk of increased induction of secondary tumors at-
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