CYP19A1 and breast carcinoma: Based on the BOLERO-2 trial in which the addition of everolimus (RAD001), an mTOR inhibitor, improved progression free survival in aromatase inhibitor resistant breast cancer, the US FDA approved the use of everolimus in combination with exemestane in patients with metastastic ER-positive breast cancer refractory to aromatase inhibitors [13–17].