A simple blood test could provide a more effective way to test for early signs of breast cancer than using an X-ray to spot a lump.
Scientists hope the blood test will be more accurate than mammograms, and will also be able to detect whether breast cancer patients are likely to relapse and what drugs their particular type of tumour will respond to.
A new study is about to begin in the UK's largest breast screening clinic at Charing Cross Hospital, London.
If the trial is successful, women could have a simple blood test every year rather than breast screening.
Professor Charles Coombes, co-investigator and Cancer Research UK's breast cancer expert, said: "When a woman has breast cancer we can tell by the DNA in their blood. But what we're trying to find out in our study is how early the signs of breast cancer show up in a blood test.
"So by looking at blood samples of women who have breast cancer diagnosed through screening we can see if the cancer is already showing in their blood."
Dr Jacqui Shaw, principal investigator, said: "This exciting research means we could one day have a blood test that detects the very early signs of cancer, meaning women could have an annual blood test rather than breast screening."