One year of adjuvant trastuzumab has been the standard treatment for human epidermal growth factor receptor 2-positive (HER2-positive) early breast cancer since the mid-2000s.1 From the outset, the expense and cardiac toxicity associated with trastuzumab use led to questioning of treatment duration (1 year), which was chosen based on a slim scientific base. Here, ERBB2 is linked to breast carcinoma.