Strategies to either escalate or de-escalate systemic therapy in early-stage HER2-positive breast cancer to improve survival outcomes and quality of life have been explored,6 such as decreasing the number of cycles of chemotherapy and/or the duration of trastuzumab,7, 8, 9, 10 increasing HER2 blockade with pertuzumab11 or neratinib,12 or switching anti-HER2 therapy to trastuzumab emtansine in patients who do not achieve a pathological complete response (pCR) following neoadjuvant therapy.13 This evidence concerns the gene ERBB2 and breast cancer.