ESR1 and breast cancer: The recent WSG-ADAPT-TP (NCT01779206) trial showed the combination of T-DM1 and endocrine therapy to be effective and allowed for the omission of standard chemotherapy without compromising 5-year invasive disease-free survival [52], suggesting further investigation of oral SERDs plus ADC combinations are warranted in trastuzumab-refractory HER2+/ER+ breast cancer.