CYP19A1 and breast cancer: The treatment of breast cancer has changed dramatically during the past 15 years, with all patients now receiving long-term antihormonal therapies, whether it is tamoxifen (EBCTCG, 1998), aromatase inhibitors (ATAC Trialists' Group, 2002), or LHRH superagonists plus tamoxifen (Emens and Davidson, 2003).