Morphological Factors and Cardiac Doses in Whole Breast Radiation for Left-sided Breast Cancer

Background: To investigate the impact of the breast size, shape, maximum heart depth (MDH), and chestwall hypotenuse (the distance connecting middle point of the sternum and the length of lung draw on the selectedtransverse CT slice) on the volumetric dose to heart with whole breast irradiation (WBI) of left-sided breastcancer patients. Materials and
Methods: Fifty-three patients with left-sided breast cancer undergoing adjuvantintensity-modulated radiotherapy (IMRT) were enrolled in the study. The primary breast size and shape, MHDand DCWH (chest wall hypotenuse) were contoured on radiotherapy (RT) planning CT slices. The dose data of heartswere obtained from the dose-volume histograms (DVHs). Data were analyzed by one-way analysis of variance(ANOVA), Student’s t-test and linear regression analysis.
Results: Breast size was independent of heart dose,whereas breast shape, MHD and DCWH were correlated with heart dose. The shapes of breasts were dividedinto four types, as the flap type, hemisphere type, cone type and pendulous type with heart mean dose being491.8±234.6cGy, 752.7±219.0cGy, 620.2±275.7cGy, and 666.1±238.0cGy, respectively. The flap type of breastsshows a strong statistically reduction in heart dose, compared to others (p=0.008 for V30 of heart). DCWHand MHD were found to be the most important parameters correlating with heart dose in WBI.
Conclusions:More attention should be paid to the heart dose of non-flap type patients. The MHD was found to be the mostimportant parameter to correlate with heart dose in tangential WBI, closely followed by the DCWH, whichcould help radiation oncologists and physicsts evaluate heart dose and design RT plan in advance.