Cardiac dosimetric evaluation of tangential VMAT technique in patients with left breast cancer after breast-conserving surgery, including internal mammary lymph node irradiation

Abstract

Objective To investigate the potential heart sparing effects of tangential volumetric modulated arc therapy (T-VMAT) by comparing its dosimetric properties with conventional wedged tangential fields (W-TF) technique and 6-field intensity-modulated radiotherapy (6F-IMRT) in the loco-regional radiotherapy of left breast cancer after conserving surgery, including internal mammary nodal irradiation. Methods Fifteen patients with left breast cancer were enrolled in this study. Three plans were generated for each patient: W-TF, 6F-IMRT and T-VMAT with two arc segments of 50°. The prescription dose to planning tumor volume (PTV) was 50 Gy in 25 fractions. Dose-volume parameters and indices of conformity were calculated and compared for the PTV and organs at risk (OAR). Results Compared with W-TF, T-VMAT not only significantly decreased Dmax, Dmean and the high dose areas (above 10 Gy) of the heart and left anterior descending branch (LAD) (P 0.05). T-VMAT also significantly decreased Dmean, V5 Gy, V10 Gy and V20 Gy of the heart, as well as the Dmean, V5 Gy and V10 Gy of LAD (P 0.05). T-VMAT achieved distinctly better target coverage and conformity, meanwhile obviously lowered hot volume of V110 compared to W-TF (P<0.05). Conclusions T-VMAT not only significantly decreased the high dose areas, but also had the trend of sparing the low dose area for the heat and LAD. Moreover, there was no significant difference for V20 Gy of ipsilateral lung and V5 Gy of contralateral breast between T-VMAT and W-TF. Key words: Breast cancer; Cardiac toxicity; Volumetric modulated arc therapy; Intensity-modulated radiotherapy