Impact of deep inspiration breath hold irradiation on dose reduction to the heart and left coronary artery in breast cancer

Objectives. Deep inspiration breath-hold (DIBH) is an effective and feasible approach to reducing the radiation dose to the heart in left-sided breast cancer radiotherapy (RT). This study aimed to assess the impact of DIBH on dose reduction to the heart and the left anterior descending coronary artery (LAD) in left-sided early breast cancer patients with intact breasts. Material and methods. We compared RT plans of 42 patients from computed tomography datasets acquired for free breathing (FB) and DIBH techniques with 6 MeV photon tangential fields. The prescribed dose was 50 Gy in 25 fractions. Results. DIBH enabled significant dose reduction to the heart and the LAD. A significantly lower mean heart dose (MHD) was observed in DIBH compared to FB planning (2.9 vs. 6.0 Gy, respectively; p < 0.0001). The considered LAD parameters, namely Dmax 0.2 cm3, mean dose, and V45Gy, were all significantly reduced in DIBH compared to FB planning (33.3 vs. 47 Gy; p < 0.0001, 16.7 vs. 30.1 Gy; p < 0.0001 and 0.5 vs 1.7 cm3; p < 0.0001, respectively). Reduction in any of the LAD dose parameters was not correlated with MHD reduction. The LAD parameters were found to be significantly reduced in the group of patients with modest MHD reduction defined as < 2.8 Gy (31.2 vs. 46.9 Gy; p = 0.0001, 15 vs. 26.9 Gy; p < 0.00001, and 0.5 vs. 1.6 Gy; p = 0.0005, respectively). Conclusions. DIBH has a pronounced impact on dose reduction to the LAD. This influence is not correlated with the MHD and is present even in patients with modest MHD reduction with DIBH.