Scientists have developed a blood test for breast cancer able to identify which patients will suffer a relapse after treatment, months before tumours are visible on hospital scans.
The test can uncover small numbers of residual cancer cells that have resisted therapy by detecting cancer DNA in the bloodstream.
Researchers at The Institute of Cancer Research, London, and The Royal Marsden NHS Foundation Trust were able to track key mutations that cancer accumulates as it develops and spreads, without the need for invasive biopsy procedures.
They hope that by deciphering the DNA code found in blood samples, it should be possible to identify the particularly mutations likely to prove lethal to that patient – and tailor treatment accordingly.
The study is an important step towards use of ‘liquid biopsies’ to revolutionise breast cancer care – by changing the way cancer is monitored in the clinic and informing treatment decisions.
Researchers 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.
By monitoring patients with blood tests taken after surgery and then every six months in follow-up, the researchers were able to predict very accurately who would suffer a relapse.
Women who tested positive for circulating tumour DNA were at 12 times the risk of relapse of those who tested negative, and the return of their cancer was detected an average of 7.9 months before any visible signs emerged.
The researchers used a technique called ‘mutation tracking’ – developing a digital PCR test that was personalised to the mutations found in an individual patient’s cancer – to identify tumour DNA in the bloodstream.
Because the researchers at the ICR and The Royal Marsden were looking for mutations common to many types of breast cancers, they found the test could be applied to all breast cancer subtypes.
The research also showed how genetic mutations build up in the cancer as it develops over time, as the leftover cancer cells grow and spread.
This reinforces the importance of detecting recurrence early so patients can have treatment before the extra mutations emerge and make the disease harder to treat. Institute of Cancer Research