Dosimetric comparison of VitalBeam(®) and Halcyon(TM) 2.0 for hypofractionated VMAT with simultaneous integrated boost treatment of early‐stage left‐sided breast cancer

PURPOSE: This study compared the quality of treatment plans for early‐stage, left‐sided breast cancer, as planned for and delivered by the Halcyon(TM) and VitalBeam(®). MATERIALS AND METHODS: Fifteen patients diagnosed with early‐stage left‐sided breast cancer, who had received VMAT with hypofractionated SIB, were recruited. All cases were planned using Halcyon(TM) comprising a dual‐layer MLC (DL‐MLC) and VitalBeam(®) with a Millennium 120 MLC (VB‐MLC). For the PTVs, the quality of coverage (QC), conformity index (CI), and homogeneity index (HI) were calculated for each plan. The dosimetric differences between the two treatment plans were statistically compared using the Wilcoxon signed‐rank test (p < 0.05). To evaluate delivery efficiency, the average delivery time for each patient's treatment plan was recorded and compared. RESULTS: For the PTVs, the two plans (DL‐MLC and VB‐MLC) were comparable in terms of the QC, CI, and HI. However, V (30Gy) and D (mean) for the heart in the DL‐MLC plan were significantly reduced by 0.49% and 14.6%, respectively, compared with those in the VB‐MLC plan (p < 0.05). The D (mean) value for the ipsilateral lung in the DL‐MLC plan significantly decreased by 5.5%, compared with that in the VB‐MLC plan (p < 0.05). In addition, the delivery times for the DL‐MLC and VB‐MLC plans were 79 ± 10 and 101 ± 11 s, respectively. CONCLUSIONS: DL‐MLC plans were found to improve OAR sparing. In particular, when treating left‐sided breast cancer via DL‐MLC plans, the risk of heart toxicity is expected to be reduced.