Is Synchronous Bilateral Breast Irradiation Using Flattening Filter-Free Beam-Based Volumetric-Modulated Arc Therapy Beneficial? A Dosimetric Study

OBJECTIVE: The aim of this study is to validate the clinical use of flattening filter-free (FFF) beam-based volumetric-modulated arc therapy (VMAT) in synchronous bilateral breast carcinoma (SBBC) patient treatments and to compare with flattening filtered (FF) beam-based VMAT. MATERIALS AND METHODS: Computed tomography images of 15 SBBC patients were taken for this study. A dose of 50 Gy in 25 fractions was prescribed to planning target volume (PTV). VMAT plans were generated using both FFF and FF 6 MV X-ray beams in Eclipse treatment planning system. PTV and organs at risk (OARs) doses were analyzed quantitatively using dose–volume histograms (DVHs) to meet plan objectives. Pretreatment point and planar dosimetry were performed. RESULTS: The findings were reported as mean ± 1 standard deviation. PTV volume receiving 95% of the prescribed dose was 95.71% ± 0.65% for FF-VMAT and 95.45% ± 1.33% for FFF-VMAT (P = 0.743). Conformity index was 1.12 ± 0.31 (FF-VMAT) and 1.12 ± 0.02 (FFF-VMAT). Right lung mean dose was 10.95 ± 1.33 Gy (FF-VMAT) and 10.60 ± 98.5 (FFF-VMAT). Left lung mean dose was 9.73 ± 1.56 (FF-VMAT) and 9.61 ± 1.53 Gy (FFF-VMAT). Tumor control probability (TCP) was 99.68% ± 0.02% (FF-VMAT) and 99.67% ± 0.01% (FFF-VMAT) (P = 0.390). Uncomplicated TCP was 98.72% ± 0.02% (FF-VMAT) and 98.72% ± 0.01% (FFF-VMAT) (P = 0.508). CONCLUSION: The planning objective parameters achieved using FFF-based VMAT showed that FFF can also be used clinically to treat bilateral breast carcinomas and the low-dose lung volumes were still lesser with FFF-VMAT plans than FF-VMAT.