ERBB2 and breast cancer: Since then, de-escalation trials of cytotoxic therapy such as PerELISA,14 PHERGain13 and WSG-ADAPT-HER2-positive/HR-negative11,12 have focused on dual HER2 blockade with trastuzumab and pertuzumab, a combination approved by FDA and EMA for the treatment of early-stage HER2-positive breast cancer.