ABSTRACT
PURPOSE: This 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 HVMAT-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). METHODS: Planning 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 HVMAT plans and a 3D-CRT plan as reference. HVMAT plans consisted of two treatment plans including 3D-CRT and VMAT. During HVMAT 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. RESULTS: Compared to the reference treatment plans, all HVMAT plans showed consistently better PTV dose coverage, conformity, and homogeneity. Additionally, OAR protection was significantly improved with several HVMAT combinations (pâ¯< 0.05). The comparison of different HVMAT 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. CONCLUSION: The HVMAT technique is an effective possibility for generating homogenous and conformal dose distributions. With the right choice of HVMAT combination, superior OAR protection is achieved compared to 3D-CRT.