UK-based scientists have developed a blood test able to identify which patients with breast cancer will suffer a relapse after treatment, months before tumours are identifiable by hospital scans.

The test, which is based on the concept of ‘mutation tracking’, looks for circulating tumour DNA in the bloodstream via a digital PCR test, and was able to detect “very accurately” which patients would suffer a relapse.

Researchers from the Institute or Cancer Research and The Royal Marsden NHS Foundation Trust took tumour and blood samples from 55 breast cancer patients with early-stage disease who had received chemotherapy followed by surgery, and who had potentially been cured of their disease. 

They found that women who tested positive for circulating tumour DNA were at 12 times the risk of relapse than those who tested negative, and the return of their cancer was detected an average of 7.9 months before any visible signs emerged.

The scientists also found that the test could be applied to all breast cancer subtypes, paving the way for so-called ‘liquid biopsies’ that could revolutionise disease monitoring and treatment decisions.

Staying a step ahead

Paul Workman, chief executive of the ICR, said the test “could help us stay a step ahead of cancer by monitoring the way it is changing and picking treatments that exploit the weakness of the particular tumour”.

Study leader Nicholas Turner, team leader in Molecular Oncology at the ICR and consultant medical oncologist at The Royal Marsden, said it will be “some years” before the test could potentially be available, “but we hope to bring this date closer by conducting much larger clinical trials starting next year”. 

“There are still challenges in implementing this technology, but digital PCR is relatively cost-effective and the information that it provides could make a real difference to breast cancer patients,” he noted.