Considering cardiovascular events in the phase III trials comparing aromatase inhibitors to tamoxifen (Table 4), there is no substantial evidence suggesting detrimental effects of aromatase inhibitors with respect to cardiovascular morbidity and mortality in early breast cancer (Jakesz et al. 2005, Boccardo et al. 2006, 2013, Kaufmann et al. 2007, Forbes et al. 2008, Colleoni et al. 2011, van de Velde et al. 2011, Bliss et al. 2012, Dubsky et al. 2012). This evidence concerns the gene CYP19A1 and breast cancer.