CYP19A1 and breast cancer: BOLERO-2 (Breast cancer trial of OraL EveROlimus- 2), a phase III study, demonstrated that the addition of everolimus to exemestane significantly prolonged the PFS from 3.2 months to 7.8 months (from 4.1 to 11.0 months by central review) in postmenopausal HR+/HER2- advanced breast cancer patients refractory to nonsteroidal aromatase inhibitor (NSAI) [16, 17].