There was no clear difference in CBC SIRs by age at first BC diagnosis in BRCA2 PV carriers, although SIRs were elevated in both groups (under age 45 years: SIR, 9.58 [95% CI, 5.10 to 16.4]; 45 years or over: SIR, 6.99 [95% CI, 4.52 to 10.3]). Here, BRCA2 is linked to breast cancer.