CYP19A1 and breast cancer: Third-generation aromatase inhibitors (AIs) such as anastrozole (1 mg/d), letrozole (2.5 mg/d), and exemestane (25 mg/d), have proven more effective than tamoxifen in upfront, switch and extended adjuvant treatments with regard to disease-free survival (DFS) and distant metastasis (DM) in postmenopausal women with hormone-sensitive early breast cancer [1-3].