Contralateral breast cancer risk in BRCA1/2-positive families needs to be adjusted for phenocopy rates particularly in second-degree untested relatives.

In the previous issue of Breast Cancer Research, Rhiem and colleagues report contralateral breast cancer risks in relatives of BRCA1/2 mutation carriers as well as those testing negative. The authors quote 25-year risks of 44.1% for BRCA1 and 33.5% for BRCA2. The risks quoted are somewhat lower than might be inferred from previous estimates in BRCA1/2 carriers, which have been as high as 40% at 10 years . This discrepancy may be explained in part by the decision to exclude index cases in which there may have been testing bias to bilateral disease. However, the authors dismiss a second bias of including many non-carriers in their analysis as 'putative' carriers.