ERBB2 and breast cancer: Trastuzumab deruxtecan received accelerated approval in 2019 and has now become the new standard of care for second-line therapy in HER2-positive BC patients who have received a prior anti-HER2 based regimen either in the metastatic setting, or in the neoadjuvant or adjuvant setting and have developed disease recurrence during or within 6 months of completing therapy.