RESUMO
PURPOSE: Flattening filter-free (FFF)-based volumetric modulated arc therapy (VMAT) has been shown to be feasible and significantly improves treatment efficiency and lung protection for synchronous bilateral breast irradiation (SBBI). This research compared the commonly used VMAT field arrangements using FFF beams. METHODS: Twenty-eight patients underwent SBBI were retrospectively enrolled to design irradiation plans using tangential arc VMAT (taVMAT), half arc VMAT (haVMAT), and large arc VMAT (laVMAT). Dosimetric and delivery parameters of all designed plans were recorded and compared. RESULTS: Comparable target volume coverage was observed for all field arrangements. taVMAT significantly reduced the dose to spinal cord and the volume covered by 5 Gy (V5Gy) and V7Gy of the lungs while decreasing the conformity index of the target volume. It also increased the volume covered by 105% of the prescription dose (V105%) and V107% of the target volume. haVMAT considerably decreased V20 Gy and V30 Gy of the lungs, mean dose (Dmean) and V30 Gy of the heart and the liver. It also notably reduced Dmean and V40 Gy of the left anterior descending coronary artery while increasing the beam-on time. laVMAT significantly reduced the mean treatment time (range, 113-117 seconds) compared with the other field arrangements. CONCLUSIONS: There were distinct differences in various dosimetric and delivery parameters for different field arrangements, highlighting the importance of selecting the appropriate field arrangement based on specific treatment goals and considerations. This study contributes valuable insights into the use of FFF-based VMAT techniques in SBBI.
