ERBB2 and breast cancer: Neratinib was first approved as a single agent by the US Food and Drug Administration (FDA) for extended adjuvant treatment of patients with early-stage, HER2-positive breast cancer following adjuvant trastuzumab-based therapy [7], and by the European Medicines Agency for patients with early-stage hormone receptor-positive HER2-overexpressed/amplified breast cancer who completed trastuzumab-based therapy less than one year ago [8].