CYP19A1 and breast cancer: In postmenopausal women, tamoxifen is replaced by aromatase inhibitor drugs, which also target the estrogen signaling pathway, such as anastrozole (Arimidex, AstraZeneca Pharmaceutics, United Kingdom) or letrozole (Femara, Novartis Pharma, Basel, Switzerland) [43], as they produce a greater reduction in breast cancer recurrence than tamoxifen alone [44].