Accordingly, Selective Estrogen Receptor Downregulators (SERDs, for example, Faslodex) have been found to be effective inhibitors of ER+ breast tumor growth but their utility is limited to their use as second or third line therapeutics in postmenopausal women with metastatic disease due to their broader impact on physiological ER signaling pathways in normal tissues [14,15]. This evidence concerns the gene ESR1 and breast neoplasm.