Hybrid Volumetric Modulated Arc Therapy With Deep Inspiration Breath Hold for Hypofractionated Bilateral Breast Irradiation: Coming Together is a Beginning

Abstract

Purpose of the present study was to explore the benefits of hybrid volumetric modulated arc therapy (H-VMAT) & deep inspiratory breath hold (DIBH) for synchronous bilateral breast cancer patients. Six patients diagnosed with bilateral breast cancer were planned for H–VMAT and dual Isocenter VMAT. On the planning CT data set planning target volume (PTV) & organs at risk (OARs) like lungs, heart, liver, celiac plexus with gastro-esophageal junction (GEJCP), left anterior descending artery (LAD), right coronary artery (RCA) were delineated using standard delineation guidelines. Dose prescribed was 40.5 Gy in 15 fractions to bilateral breast. PTV & OARs dosimetric parameters were compared using non-parametric Mann Whitney test. The monitor units (MU) and beam-on time were used as an objective measure to evaluate delivery efficiency. Coverage, conformity index, and homogeneity index in both techniques were comparable. However, H-VMAT achieved better sparing of heart & lung at low dose regions (V5Gy to heart was 23.4+10.1 & 39.5+16.3; p<0.01), V5Gy to lungs was 41.3+8.7 & 59.9+6.9; p<0.01). In addition, V20Gy to lungs and Dmean to GEJCP were better with H-VMAT (9.4+3.7 & 14.3+3.9; 1.9+1.4 & 2.9+2.1, respectively). There were no significant differences in relatively high and intermediate dose regions in both techniques for OARs (LAD, RCA, heart, liver). MU was comparable, while beam-on time was higher in H-VMAT. Overall, H-VMAT reduces low dose bath and is comparable in terms of high and intermediate dose to OARs. These dosimetric benefits have the potential to reduce not just late radiation toxicity but acute toxicities like radiation induced nausea and vomiting (RINV) and pneumonitis in the setting of hypofractionation.