In a human-in-mouse model of ER+/HER2+ breast cancer, adjuvant paclitaxel plus trastuzumab ± pertuzumab for 4 weeks, followed by “extended adjuvant therapy” with fulvestrant plus neratinib for an additional 4 weeks, was associated with maintenance of a complete response (CR), whereas subjects treated with extended fulvestrant alone relapsed rapidly51. This evidence concerns the gene ESR1 and breast cancer.