A new liquid biopsy has been shown to detect the return and spread of breast cancer months before symptoms emerge or hospital scanners can find the disease.

The test, developed by researchers at the Institute of Cancer Research (ICR) and the Royal Marsden NHS Foundation Trust, was found to detect levels of cancer DNA circulating in the blood an average of 10.7 months before clinical diagnosis in patients who had relapsed during the study’s three-year follow-up period.

The test works in all types of breast cancer, and can detect early signs of the disease metastasising around the body outside of the brain.

ICR professor of molecular oncology Nicholas Turner said: “These new blood tests can work out which patients are at risk of relapse much more accurately than we have done before, identifying the earliest signs of relapse almost a year before the patient will clinically relapse.”

Turner and his colleagues studied 101 women with breast cancer across five hospitals. Each woman was given a personalised blood test tailored to the makeup of their tumour to enable the levels of cancer DNA in their bloodstream to be monitored.

By analysing cancer DNA from tumour samples collected before treatment, the researchers were able to identify mutations that could distinguish this DNA from all other DNA in the blood and track its levels over time. In the 101 patients, 165 different trackable mutations were found, with 78 patients having one mutation and 23 having multiple mutations. Blood samples were collected from the participants every three months during their first year after treatment, and then every six months for up to five years after treatment.

To assess the test’s ability to detect recurrence at a molecular level in different breast cancer variations, the researchers combined the data from this study with a previous proof-of-principle experiment with 43 participants.

At a three-year follow-up, 29 of the 144 total patients had experienced a relapse in their condition. The test was able to detect cancer DNA in the blood of 23 of these patients prior to their relapse, with signs of recurrence spotted an average of 10.7 months before their clinical diagnosis.

Turner said: “We hope that by identifying relapse much earlier we will be able to treat it much more effectively than we can do now, perhaps even prevent some people from relapsing. But we will now need clinical trials to assess whether we can use these blood tests to improve patient outcome. We have launched the first of these studies already, and hope to launch large studies in the future.”

Trials are now underway to assess new treatments alongside this test in triple negative breast cancer.