The BOLERO-2 study showed the efficacy of the combination of mTOR-inhibitor everolimus plus exemestane in patients with ER-positive/HER2-negative advanced breast cancer (BC) resistant to non-steroidal aromatase inhibitors (NSAIs), with a significant improvement in progression-free survival (PFS) in comparison to exemestane monotherapy (7.8 months versus 3.2 months) [3]. Here, CYP19A1 is linked to breast cancer.