A blood test that can detect breast cancer decades before the disease develops could be available in five years, scientists have announced.
By Rebecca Smith, Medical Editor
8:08PM BST 30 Apr 2012
The test could help doctors to identify women at high risk of the disease allowing them to take preventive medicines and switch to healthier lifestyles.
Researchers have identified a 'genetic switch', carried by one in five women, that doubles their risk of developing breast cancer.
Experts described the breakthrough by scientists at Imperial College London as "exciting" and said signs of the disease could be detected "many decades in advance".
Dr James Flanagan, who led the new research, said the test could be available in five to ten years.
The 'genetic switch' is influenced by lifestyle factors such as alcohol, smoking, pollution, and hormones including HRT.
Carrying the genetic alterations increase a woman's lifetime risk of developing breast cancer from one in eight in the general population to one in four.
These tiny genetic changes could be detected in blood samples years before symptoms of breast cancer developed.
Scientists analysed blood samples from 1,380 women of various ages, 640 of whom went on to develop breast cancer.
On average, the blood tests were carried out three years before diagnosis. In some cases they pre-dated the discovery of breast cancer by up to 11 years.
The results were especially clear in blood samples from women under the age of 60.
Around 49,000 people are diagnosed with breast cancer each year and almost 12,000 die annually in Britain.
The changes are also associated with lymphoma and leukaemia meaning the test could have implications in other cancers.
A strong association was found between molecular changes in a white blood cell gene called ATM and breast cancer risk.
Dr Flanagan said: 'We are working towards prevention. If we can identify women at high risk of cancer we can work towards preventing it and could reduce the incidence of breast cancer quite dramatically.
"We have found one marker, we need to work towards finding them all and then we will have a more useful test."
The findings are published in the journal Cancer Research.
Baroness Delyth Morgan, chief executive of Breast Cancer Campaign, said: "Dr Flanagan's research into epigenetics is so exciting because it suggests that there is every possibility the risk of developing breast cancer could be decided many decades in advance.
"By piecing together how this happens, we can look at ways of preventing the disease and detecting it earlier to give people the best possible chance of survival."
Last month researchers announced that they had discovered that breast cancer was not a single disease but there were fact ten distinct genetic types.
This means that treatment can be tailored to the genetic profile of the specific type meaning drugs will work better, with fewer side effects.