BRCA2 and breast cancer: By contrast, only four studies (eTable 1) have reported breast cancer risk estimates for Asian carriers of BRCA1 and BRCA2 PV, of which two also estimated ovarian cancer risks.9, 10, 11, 12 These cumulative cancer risk estimates are imprecise and there was substantial variability in the relative risk estimates between studies, likely due to differences in sampling and analytical methods.