BRCA1 and breast cancer: There was some evidence for a nonbreast/ovarian cancer risk difference by age at first BC diagnosis in noncarriers (under 45 years: SIR, 1.68 [95% CI, 1.39 to 2.01]; 45 years or over: SIR, 1.15 [95% CI, 1.02 to 1.28]), which we did not observe for BRCA1/BRCA2 PV carriers.