Researchers say a new blood test could potentially help predict breast cancer relapses earlier, and help refine treatments.

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.

While the test is not yet available to the public, and likely will not be for years to come, researchers are hopeful that it could help refine personalised treatments for cancer and perhaps lead scientists further down the path of finding a cure one day.

"We have shown how a simple blood test has the potential to accurately predict which patients will relapse from breast cancer, much earlier than we can currently," said study author Nicholas Turner, team leader in molecular oncology at The Institute of Cancer Research, London.

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 technique uses personalised digital polymerase chain reaction (dPCR) tests to track mutations and could be applied to all subtypes of breast cancer, the study said.

Turner said there are some technical challenges to implementing the technology, "but digital PCR is relatively cost-effective and the information that it provides could make a real difference to breast cancer patients".