Would you give/omit regional nodal irradiation in low nodal burden ER- Her2+ disease s/p BCS with SLNB?

When I evaluate patients in this situation, BCS + SLN with positive node, I tend to think about the decision as to the whole breast RT+/- RNI and use AMAROS/Z011 to frame my decision making.

In an ER-negative patient, I would favor RNI, extrapolating from MA20 (where patients had an ALND, and 85% 1-3 nodes involved) that showed a survival advantage for ER- patients.

The study you note is a secondary analysis of a trial (Gingras et al., PMID 28376188). The RNI patients had worse features (higher nodal burden and more frequently had tumors larger than 2 cm), so I would not use this as a rationale to exclude RNI.