I agree with others that in the era of effective anti-HER2 systemic agents, the likelihood of in-breast recurrence can be very low for HER2 positive breast cancer patients undergoing breast conserving therapy. On the other hand, there is little to no prospective data regarding the efficacy of APBI. ...

With respect to HER2+ disease, I do offer partial breast irradiation if other features are appropriate. In early stage patients receiving HER2 targeted therapy, data from the APT trial showed low rates of locoregional recurrence supporting partial breast irradiation for this cohort of patients. In t...