Many women with a faulty breast cancer gene could be at greater risk of the disease due to extra 'risk amplifying' genes, according to research published in the American Journal of Human Genetics today.
Cancer Research UK scientists have found that common versions of two genes - FGFR2 and TNRC9 - known to increase breast cancer risk in the general population - also increase the risk in women carrying damaged versions of the BRCA2 gene.
Around one in eighteen women will develop breast cancer by the age of 65. On average, half of women carrying a faulty BRCA2 gene will develop the disease by the age of 70.
This study found that particular combinations of the FGFR2 and TNRC9 genes modify breast cancer risk in BRCA2 mutation carriers.
One per cent of BRCA2 mutation carriers have the highest risk combination of FGFR2 and TNRC9 genes. Seven in every 10 women in this category are predicted to develop breast cancer.
Around twenty percent of the BRCA2 mutation carriers have the lowest risk combination of the FGFR2 and TNRC9 genes. The researchers found that their risk is lowered so four in every 10 women in this category are expected to develop the disease.
These findings are the first step in a series of studies hunting for breast cancer susceptibility genes, which aims to better monitor and treat women with a family history of the disease.