Data from the Edinburgh Breast Unit demonstrate high response rates with reductions in tumor volume greater than 80% in some cases of postmenopausal women with estrogen receptor-rich tumors after just three months of NET, while Fontein et al. demonstrated improved clinical response and breast conservation rates following six months of neoadjuvant endocrine therapy when compared to three [24, 25]. This evidence concerns the gene ESR1 and neoplasm.