There are several shortcoming of our analysis. We assumed a rigid body model (i.e., that the relative position of the chest/breast and heart was constant). This clearly is not the case. Nevertheless, this is a reasonable assumption, given the goals of the analysis. Surface has been proven to be a reasonable surrogate for DIBH patient setup from a port film analysis in Tang et al. (20) A total of 270 port films from 50 patients was analyzed to assess patient surface based setup accuracy. The distance between the field edge and the anterior pericardial shadow was measured on port films and corresponding digitally reconstructed radiographs (DRR). The reported discrepancy was 0.2±0.19 cm, which was fairly reproducible. On the other hand, it was reported that the interfraction DIBH motion of the heart had reproducibility of 3 mm in the anterior–posterior (AP), 7 mm in the superior–inferior (SI), and 3 mm in the left–right (LR) directions. (24) Moderate correlation was found between surface and heart setup errors in Alderliesten et al.: (13) R2=0.53, 0.37, 0.64 in AP, SI, and LR directions, respectively. Therefore, an inclusion of a more sophisticated model (i.e., deformable registration) might make the analysis more accurate. However, one should carefully evaluate the trade‐off between the complexity of the analysis and the degree of the benefit. In cases where the IMNs are targeted and where they are receiving (nearly or) full dose, they tend to be close to the field edge. If the beam is too deep, the nodal targets remain in the field, but the dose does not increase. Conversely, if the beam is too shallow, the dose can decline rapidly due to the proximity to the beam edge. Thus, the dosimetric consequences of breath‐hold motions are not symmetric (underdosage is more common than overdosage). Similarly, for structures that are well out of the planned beams, such as the heart in most of our cases, the exact reverse occurs. If the beam is too shallow, the dose remains low, and if the beam is too deep, the dose can increase (motion tends to increase the cardiac dose; which is to say that overdosage is more common than underdosage).