A new blood test has been developed that can identify which breast cancer patients will suffer a relapse after treatment - months before tumours can be detected by hospital scans.
The test can reveal small numbers of residual cancer cells that have resisted therapy by detecting cancer DNA in the bloodstream. It means that women with the condition could be spared the need for invasive biopsy procedures.
It is hoped the study, which was carried out at The Institute of Cancer Research (ICR), London, and The Royal Marsden NHS Foundation Trust, could lead to 'liquid biopsies' that revolutionise breast cancer care by changing the way the condition is monitored in the clinic and informing treatment decisions.
Tumour and blood samples were taken from 55 breast cancer patients in the early stages of the disease who had received chemotherapy followed by surgery, and who had potentially been cured.
Patients were monitored by having a blood test taken after surgery and at regular six-month intervals, and researchers were able to predict very accurately who would suffer a relapse.
Women who tested positive for circulating tumour DNA were 12 times more likely to suffer a relapse compared to those who tested negative, while the return of their cancer was detected an average of 7.9 months before any visible signs emerged.
A technique known as mutation tracking was used to identify tumour DNA in the bloodstream. This involved creating a digital polymerase chain reaction test that was personalised to the mutations found in an individual patient's cancer.
Study leader Dr Nicholas Turner, team leader in molecular oncology at the ICR and consultant medical oncologist at The Royal Marsden, said: "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.
"We also used blood tests to build a picture of how the cancer was evolving over time, and this information could be invaluable to help doctors select the correct drugs to treat the cancer."