BRCA1 and breast cancer: In our main model we used penetrance figures of 59 % for BRCA1 and 51 % for BRCA2 based on average cumulative risk of female breast cancer modelled over all possible modifiers for carriers born after 1950 [15], but also included ranges of 57-71 % for BRCA1 [18–20] and 45–87.5 % [21, 22] for BRCA2 based on other literature findings.