Tables published by Royal Marsden NHS
The table above shows the cancer risk percentages for breast and ovarian cancer for both BRCA1 and BRCA2 mutation carriers. The second part of the table details the risk of developing breast cancer by age.
According to these data, carrying a BRCA1 mutation may confer a higher risk of breast cancer and a considerably higher risk of ovarian cancer than compared to BRCA2 mutation carriers. In other words, BRCA1 mutations may be more penetrant than BRCA2 gene mutations.
BRCA gene mutations also become more penetrant with increasing age, meaning that cancers associated with these mutations are increasingly likely to manifest as we get older. This explains why there is a sharp rise in the incidence of breast and ovarian cancers in BRCA mutation carriers between the ages of 40-50. More specifically, the risk of ovarian cancer in women who carry a BRCA1 mutation rises significantly after age 40, and after age 45 for BRCA2, as can be seen in the above table.
The second part of the table details the risk of developing breast cancer between the age of 20-25 up until age 66-70 for both BRCA1 and BRCA2 mutations. Looking at these data, it is possible to see that the younger your current age, the greater your approximate remaining lifetime risk (up to 80 years old) is for developing breast cancer. For example, if you’re 30 you have a large remaining risk for the rest of your lifetime, whereas if you’re 65 you have a smaller remaining risk.
Interestingly, we can see from this table that between the ages of 56-70, the remaining lifetime risk of developing breast cancer for BRCA1 mutation carriers is lower than that of BRCA2 mutation carriers. The reason for this is that BRCA1 mutations are more penetrant at younger ages than BRCA2 and, therefore, BRCA1-associated breast cancer tends to occur at a younger age than BRCA2. As a result, we see more cancers caused by inherited BRCA2 mutations in an ageing population.
With regard to cancer risks associated with BRCA gene mutations in men, BRCA2 mutations confer a higher lifetime risk (5-10%) for breast cancer in males than BRCA1 mutations (0.1-1%) and a higher lifetime risk of prostate cancer in BRCA2 males (20-25%) than BRCA1 mutations (~10%, similar to population risk).