BRCA1 and breast cancer: The mean NNT for statistically significant outcomes showed that 5.6 (4.2 to 11.8) and 14.5 (9.5 to 30.3) RRSOs are needed to prevent one death from BC in BC-affected BRCA1 and BRCA2 carriers combined and one death from BC in BC-affected BRCA1 carriers alone, respectively (Table 4).