Table 2.

Proportion of first-degree relatives with breast cancer of a proven BRCA1 or BRCA2 mutation carrier who test negative for the family mutation, by age group

Age rangeBRCA1BRCA2BRCA1 and BRCA2BRCA1/2 proportion of carriers developing their first breast cancer for each decade in age groupPopulation breast cancer rates per decade in age groupRatio of rates in age group compared with populationProportion of 50% expected to test negative if no other factors involved
18–290/80/30/113%0.05%600:10.016%
30–392/433/405/83 (6%)15%0.5%30:13.2%
40–496/468/4814/94 (15%)30%1.5%20:14.8%
50–5910/299/3719/66 (28.8%)15%2.7%6:115%
60–805/157/2112/36 (33%)25%5.8%4:118.9%
Total23/141 (16.3%)26/149 (17.5%)49/290