In the TH3RESA trial patients with HER2+ unresectable locally advanced or recurrent BC or metastatic BC who had been treated with two or more HER2-directed regimens, including trastuzumab and lapatinib, were randomized to receive T-DM1 or treatment of physician’s choice (Krop et al. [27]). This evidence concerns the gene ERBB2 and breast cancer.