BRCA1 and breast cancer: Breast cancer incidence rate showed no significant associations with MRI percent dense volume or Cumulus/Visual percent dense area, except when the analyses were adjusted for BRCA1 and BRCA2 genotype/carrier probability (Upper two quartiles vs lower two quartiles: IRR (incidence rate ratio) = 2.04 (1.16 to 3.59) P = 0.013 for MRI; IRR = 2.24 (1.18 to 4.26) P = 0.014 for VA).