The development of targeted therapies for cancers, such as trastuzumab (against HER2‐positive breast cancer) 5, 6, tamoxifen (against estrogen receptor‐positive breast cancer) 7 and cetuximab (against EGFR‐positive non‐small‐cell lung carcinoma) 8, has a strong positive response on improving disease‐free survival and overall survival for cancer patients. This evidence concerns the gene ESR1 and cancer.