While in some cancer types, such as glioblastoma [3] or ovarian cancer [4], the majority of patients undergo relapse (around 100% for glioblastoma and 85% for ovarian), for other tumors types, such as estrogen receptor positive breast cancer or prostate cancer, the proportions are sensibly lower (around 10–20%) [5,6]. This evidence concerns the gene ESR1 and glioblastoma.