Breathing adapted radiation therapy in comparison with prone position to reduce the doses to the heart, left anterior descending coronary artery, and contralateral breast in whole breast radiation therapy
Abstract: Purpose: To compare 3 different treatment positions in whole breast radiation therapy in terms of target volume coverage and doses to the organs at risk (OAR).Methods and materials: Thirty-four breast cancer (BC) patients (17 right-sided and 17 left-sided) were included in this dosimetric planning study. They all underwent a computed tomography (CT) scan in standard supine position in free-breathing (FB), supine position with gating in deep inspiratory breath hold (DIBH)(G), and prone position (P). Three-dimensional treatment plans were made for all 3 CTs. Target coverage and OAR sparing were evaluated.Results: Breast volumes varied between 209 and 2814 cm3. The target coverage, expressed as the mean volume of the breast receiving at least 95% of the prescription dose, was similar for the 3 treatment positions. The mean lung dose and the volume of the lungs receiving >20 Gy were significantly lower in P (1.7 Gy; 2.3%) compared with G (3.4 Gy; 5.6%; P < .0001) and FB (4 Gy; 7.3%; P < .0001). The volume of the contralateral breast receiving >5 Gy was significantly lower in G (P = .001) or FB (P = .004) versus prone. The supine position with gating in DIBH significantly reduced the volume of the heart receiving >30 Gy (V30heart), the mean heart (Dheart), and mean left anterior descending coronary artery (LAD) dose (DLAD) for left-sided BC patients (V30heart 0.9%, Dheart 1.6 Gy, DLAD 22.4 Gy) with respect to FB (V30heart 4.3%, Dheart 3.5 Gy, DLAD 30.9 Gy)(V30heart and mean Dheart: P ≤ .0001; mean DLAD: P = .008) and P (V30heart 7.9%, Dheart 5.4 Gy, DLAD 36.4 Gy)(V30heart and mean Dheart: P = .0004; mean DLAD: P = .01).Conclusions: The coverage of the planning target volume breast was equal for the 3 treatment positions. The lowest doses to the lungs were achieved in prone. The heart, LAD, and contralateral breast were best spared in the supine position with gating in DIBH.