CYP19A1 and breast cancer: 2007; Paridaens et al. 2008). As an adjuvant endocrine therapy, EXE irreversibly inhibits the aromatase‐mediated production of estrogens from androgen precursors, a process known as aromatization (Hong et al. 2007). A previous pharmacokinetics study found that the maximum plasma concentration of EXE in postmenopausal women with a prior history of breast cancer ranged from 3.0 to 15.6 ng/mL following 2 weeks of oral dosing (25 mg/day) while the maximum amount of its 17β‐DHE metabolite varied 7‐fold with reported values of 0.22–1.58 ng/mL (Traina et al. 2008).