CYP19A1 and breast cancer: Tamoxifen and raloxifene, both SERMs, as well as two aromatase inhibitors (AIs), exemestane and anastrozole, have been shown in randomized controlled trials to significantly reduce breast cancer incidence in women at increased risk of the disease.30–33,36,37 The SERMs are US FDA approved for this indication in postmenopausal women, although only tamoxifen has been studied and received an indication for breast cancer risk reduction in premenopausal women.