Breast cancer early warning blood test

Scientists have identified a molecular ‘switch’ in blood samples that increases a woman's chances of having breast cancer.

The marker is associated with the BRCA1 breast cancer gene, but was also found in women without the mutation who went on to develop the disease.

About 10% of breast cancers are caused by BRCA1 and BRCA2 gene variants inherited from parents, leaving 90% of cases unexplained.

A woman with the BRCA1 gene has an 85% risk of developing breast cancer, leading some carriers to take the drastic step of prophylactic bilateral mastectomy.

But until now there has been no reliable way of predicting the likelihood of non-inherited breast cancer.

The ‘switch’ discovered by scientists is part of the process by which certain molecules acting on DNA cause genes to be turned on or off.

Lead researcher Professor Martin Widschwendter, from University College London, said: "We identified an