You make a good point about not relying on mean heart dose (MHD) to tell the entire story in breast DIBH. Many DIBH dosimetric studies do include contours for LAD and report on the dose to this region. It is important to review and report metrics other than MHD. While it may be easier for a planner to not include the additional contour, it does make sense to me to contour sensitive sub-volumes of the heart.