BRCA2 and breast cancer: As shown in Table 3, all four risk groups of the HBOC study showed a higher incidence of bilateral BC compared to the general population, although only in the group of BRCA2 positives the difference reached statistical significance (7.6% vs 1.8%; p = 0.021, OR = 4.3; 95% CI = 1.3 to 11.4).