What dose constraints do you apply to the LAD for lung SBRT?

This is a great question and one that does not yet have a clear answer from SBRT toxicity outcomes data. Practically, I think we start with contouring the nearby coronaries (which is not such an easy task to broadly implement from a workflow standpoint!) and evaluating the low to moderate isodose lines and conformality to be sure when the target is not immediately adjacent that unnecessary spill is not occurring over a coronary segment. The greater challenge is when the target is immediately adjacent or there is PTV overlap with the pericardium or epicardial surface and a coverage vs OAR decision needs to be made. This can be challenging, particularly for patients at high cardiopulmonary risk in the non-operable setting. So the short answer...

ALARA while keeping the R50 & D2cm as compact and symmetric as possible. I keep the PTV overlap with LAD <105%. I never reduce the PTV less than 5 mm, unless the tumor can be tracked during the entire beam-on time with MRgRT (3 mm).