ERBB2 and breast cancer: In an indirect way, our data also allow inferences about the effect of endocrine therapy in HER2+ BC patients not treated with anti-HER2 therapy: it would have been possible that the flattening effect of endocrine therapy on the early hazard of recurrence of HR+ patients that was seen in HER2-unknown (that is mostly HER2-) cohorts [8,9,11] is not seen if the HER2 epitope is not targeted as well, thus resulting in a similar early peak in HER2+ HR+ patients as seen in HER2+ HR- patients.