Blood test predicts breast cancer relapse

Scientists have developed a blood test that can predict several months in advance which breast cancer patients will relapse.

The researchers hope the test, which detects cancer cells that have been left behind after treatment, could lead to earlier interventions in high-risk patients.

'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 lead author Dr Nicholas Turner, a Consultant Medical Oncologist at the Royal Marsden NHS Foundation Trust.

The study, published in Science Translational Medicine, looked at 55 patients with early-diagnosed breast cancer, who had all undergone surgery followed by chemotherapy. The researchers took blood samples from these patients every six months for two years to look for circulating tumour (ct)DNA.

Women who tested positive for ctDNA were found to be 12 times more likely to relapse than those who tested negative. Using this test, the researchers were able to accurately predict relapse in 12 out of the 15 patients who relapsed.

The test was also capable of predicting the relapse, on average, 7.9 months before visible signs were picked up by clinics.

After treatment, it is difficult to identify whether all cancerous cells have been removed from a patient. Cancerous cells have almost identical DNA to all other body cells, the only difference being a small number of mutations responsible for causing the cells to become cancerous.

To overcome this, the scientists used a technique called 'mutation tracking' — a polymerase chain reaction (PCR) test which is personalised to the mutations of an individual patient's cancer DNA. The test screened the blood for DNA with these mutations. Any DNA in the blood with these mutations must have been released by cancer cells remaining after the initial round of treatment.

As well as being used to predict relapse, the test will allow scientists to track further mutations that develop in cancers over time, the researchers say. This knowledge could help personalise treatment, as it would allow the tailoring of treatment to the genetic make-up of an individual's cancer.

Professor Paul Workman, Chief Executive of the Institute of Cancer Research, London, said: 'We are moving into an era of personalised medicine for cancer patients. This 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.'

Dr Nick Peel, from Cancer Research UK, said: 'Finding less invasive ways of diagnosing and monitoring cancer is really important and blood samples have emerged as one possible way of gathering crucial information about a patient's disease.'

He added: 'But there is some way to go before this could be developed into a test that doctors could use routinely, and doing so is never simple.'