Predictive blood test hailed as ‘incredibly exciting’ breast cancer breakthrough

A new blood test can predict the risk of breast cancer returning three years before any tumours show up on scans in an “incredibly exciting” breakthrough that could help more women beat the disease for good.

More than 2 million women are diagnosed every year with breast cancer, the most prevalent type of the disease. Although treatment has improved in recent decades, the cancer often returns, and if it does, it is usually at a more advanced stage.

But now research presented to the world’s largest cancer conference has shown that a personalised liquid biopsy could provide a very early warning sign that cancer is returning. Results from a trial of the tests, revealed at the American Society of Clinical Oncology annual meeting in Chicago, suggest they may help reveal which women need preventive ­therapy and which patients can be spared it.

The test detects minuscule amounts of cancer DNA in the bloodstream. Trial results show it is so sensitive that it can accurately predict the risk of cancer coming back, months or even years before the usual signs or symptoms start to emerge.

Researchers at the Breast Cancer Now Toby Robins research centre in London were able to identify every patient in the trial who later went on to relapse. The average time to relapse was 15 months; the longest 41 months.

“Early detection is one of our greatest weapons against breast cancer and these initial findings, which suggest tests could be able to detect signs of breast cancer recurrence over a year before symptoms emerge, are incredibly exciting,” said Simon Vincent, director of research at Breast Cancer Now, which helped fund the trial.

“While this research is still in its early stages, catching breast cancer recurrence earlier means treatment is much more likely to destroy the cancer and stop it spreading to other parts of the body, at which point it becomes incurable.”

Experts hope the findings will result in a strategy in which treatment can be started much earlier. The ultra-sensitive liquid biopsy works by finding circulating tumour DNA (ctDNA) that is released into the bloodstream by cancer cells.

“Breast cancer cells can remain in the body after surgery and other treatments but there can be so few of these cells that they are undetectable on follow-up scans,” said Isaac Garcia-Murillas, the study’s lead author at the Institute of Cancer Research (ICR) in London. “These cells can cause breast cancer patients to relapse many years after their initial treatment.”

Previous research has suggested ctDNA blood tests can identify relapse before it can be seen on a scan. However, these tests tend to use a technique called whole exome sequencing that typically looks for between 16 and 50 mutations. The new test uses whole genome sequencing and searches for 1,800 mutations, making it much more sensitive.

Researchers analysed blood from 78 patients with different types of breast cancer. The new test correctly flagged a high risk of recurrence in all 11 of the patients who relapsed during the five-year trial. All 60 women in whom the test did not find ctDNA did not relapse, meaning there were also no false negatives.

Three more patients had ctDNA detected once, but further tests showed it had disappeared. The ICR did not provide full data for the remaining four patients.

Prof Kristian Helin, the ICR’s chief executive, said: “Breast cancer is much easier to treat before it spreads to other parts of the body, so it is vital to be able to detect signs of recurrence as early as possible to give people the best chance of survival.

“It is very exciting to see advances in technology that can detect cancer cells and DNA with greater sensitivity to pick up residual disease or detect the early signs of breast cancer recurrence while a cure is still possible. These approaches are having a transformative effect on cancer diagnosis.”