Cancer Research UK scientists have found two new regions of the genome that alter a woman's risk of breast cancer, according to a study in Nature Genetics today.
One of the newly-identified regions of DNA appears to increase the risk of breast cancer by as much as 23%, while the other seems to have a beneficial protective effect, reducing the risk by up to 11%. Both are believed to contain mutant genes influencing susceptibility to the disease.
The study involved more than 40,000 women with breast cancer and the same number without the disease, with the scientists comparing suspect regions of the women's DNA.
More than 100 scientists from 16 countries took part in the international study, which was led by Cancer Research UK.
The organisation's director of cancer information, Dr Lesley Walker, said: "This study brings us a step closer to creating a powerful genetic test for breast cancer.
"If we can identify women who are more likely to get the disease and if we can work out how high this risk is, doctors can make informed decisions about how to stop them getting breast cancer in the first place."
Breast cancer is the most common cancer in the UK, with more than 45,500 new cases diagnosed each year.