ERBB2 and breast cancer: T-DM1 is an antibody-drug conjugate (ADC), which drives the chemotherapeutic agent directly to HER2-expressing cells through the driver trastuzumab [8]. Its safety and efficacy were evaluated in the EMILIA trial, in which patients with metastatic BC who received prior anti-HER2 therapy had a median PFS and OS significantly longer with T-DM1 versus lapatinib plus capecitabine [9].