Positive results from the phase III Breast Cancer Trials of Oral Everolimus 2 (BOLERO-2) trial led to the approval of everolimus, an mTOR inhibitor, in combination with second-line exemestane in postmenopausal women with HR+, HER2− advanced breast cancer that progressed during prior nonsteroidal aromatase inhibitor therapy [14, 15]. This evidence concerns the gene HR and breast cancer.