BRCA1 and breast cancer: Most of the studies that compared M alone with M + US were performed in countries highly populated by Caucasians (United States and Sweden).3,30,34,40,42,49 Five of the eight studies comparing M alone and M + US in patients with dense breasts provided data for the presence of common breast cancer risk factor, which included BRCA1/2 mutations, family history, personal breast cancer history, use of hormone therapy, etc.3,30,34,42,49 (Supplementary Table S1).