An experimental blood test may be able to predict whether a woman with breast cancer will suffer a relapse months before new tumours become detectable on scans.
The technology, described in the journal Science Translational Medicine, works by detecting cancer DNA that circulates in the bloodstream.
Scientists took tumour and blood samples from 55 breast cancer patients with early-stage disease. Each had received chemotherapy and surgery to remove the cancer.
The blood test was administered following surgery and every six months afterward as a follow-up.
Of the 15 women whose cancer returned, the test accurately predicted that relapse in 12 of them.
The test also detected cancer an average of about eight months earlier than the tumours were visibly detectable on conventional scans.
The test is not yet available to the public and likely will not be for years to come.