GENETICS OF BREAST CANCER

Scientists have discovered new gene variants that may increase the risk of developing breast cancer.

International researchers say 65 gene variants predispose an individual to breast cancer, with a further 10 gene variants increasing the risk of estrogen-receptor negative breast cancers that are harder to treat because they do not respond to hormonal therapies, such as the drug tamoxifen.

The discoveries bring the number of known variants associated with breast cancer from 107 to 179 – around a 60% increase.

Together, these represent about 18% of the extra risk faced by women with a family history of breast cancer.

Faulty Genes 

Breast cancer is caused by the interplay of genetic variants and environmental factors.

A rare fault, or mutation, in certain genes – such as BRCA1 and BRCA2 – confer a high risk of the disease. Gene variants in other areas may confer a smaller risk.

Some of the variants are carried by 1 woman in 100, while others are carried by more than half of women.

While each individual variant might pose a modest risk, additional variants can multiply the effect, causing a considerable increase in the overall risk of breast cancer, the scientists say.

International Research 

The findings, published in the journals Nature and Nature Genetics, add significantly to the understanding of how breast cancer can be inherited.

They are the result of work by the OncoArray Consortium, an investigation involving 550 researchers from around 300 different institutions based in six continents.

In total, they analysed genetic data from 275,000 women, of whom 146,000 had been diagnosed with breast cancer.

An "Exciting Step Forward" 

Commenting on the findings in an emailed statement, Baroness Delyth Morgan, chief executive of Breast Cancer Now, says: "This is another exciting step forward in our understanding of the genetic causes of breast cancer.

"These gene changes now have the potential to be incorporated into existing models to more accurately predict an individual's risk, and to improve both prevention and early detection of the disease.

"Crucially, the discovery of 10 new genetic variants that predispose women to ER-negative breast cancer could be particularly important. This form of the disease cannot be treated with hormone therapies and that these findings could lead to better prevention, earlier detection and possibly even more effective treatments for these patients is very promising.

"Amid increasing incidence, we need to do much more to prevent breast cancer. We now eagerly await further studies to unpick why these variants increase a person's risk and to understand whether they could be added to existing risk models to improve the way we prevent, predict and detect the disease in the clinic."

SOURCES:

Identification of ten variants associated with risk of estrogen-receptor-negative breast cancer, Nature Genetics Association analysis identifies 65 new breast cancer risk loci, Nature