Patients who have been treated for pancreatic cancer could benefit from a newly developed blood test that could identify tiny traces of the disease often missed by scans. 

The highly sensitive test has been developed by a team based at Northwestern Medicine in Chicago who followed 106 pancreatic cancer patients from initial diagnosis through chemotherapy and surgery. 

The new highly sensitive blood test - digital droplet PCR (ddPCR) - detected signs of cancer in nearly four times as many patients as conventional next-generation sequencing tests (NGS), which are more commonly used.

Both types of test search for traces of DNA shed by cancer cells into the bloodstream which can act as an early warning sign that cancer is present or may return. 

The new test looks solely for the presence of KRAS, a genetic mutation that drives more than 90 per cent of pancreatic cancers.

The study, published in Clinical Cancer Research, found that even after chemotherapy and surgery, ddPCR continued detecting cancer in most patients, while NGS and standard testing didn’t.

It means that it could potentially help specialists identify patients whose disease is more likely to return - even when scans and other measuring tools appear reassuring. 

When it comes to pancreatic cancer, early detection is key - both when it is first diagnosed and when seeing if it has metastasised elsewhere in the body. 

Around 11,500 people are diagnosed with pancreatic cancer in the UK each year, between 10 and 20 per cent of whom are stage two, but the disease is notoriously difficult both to diagnose and treat. 

Common symptoms of the incurable cancer - dubbed the 'silent killer' - include jaundice (when the skin and eyes take on a yellowish tinge), reduced appetite, weight loss, fatigue, a high temperature, feeling or being sick, diarrhoea and constipation. 

As it is often caught very late, when treatment options are limited, only 10 per cent of patients live longer than five years after diagnosis - with more than half dying within three months of finding out that they have the illness.

At present, the disease is incurable, with life expectancy just five years from initial diagnosis. Just one in four patients live more than a year. 

Harry Potter star Alan Rickman died in 2016 from pancreatic cancer aged 69, surviving just six months after his diagnosis.

Thanks to ddPCR the Northwestern Medicine team were able to identify a previously hidden group of high-risk patients whose cancer was missed by standard NGS. 

That group survived a median of 27 months after diagnosis, compared with 41 months among patients who tested negative on both the ddPCR and NGS tests.

Speaking of people whose pancreatic cancer returns after surgery, study senior author Dr. Akhil Chawla said: 'In these patients, circulating tumor DNA levels are often extremely low and difficult to detect.

'Many patients and families ask me, "How do we know if the treatment is working?" This research is part of trying to answer that question more precisely.' 

The blood test comes shortly after a new treatment, daraxonrasib, was found to be able to target the KRAS mutation - a huge advancement in the treatment of pancreatic cancer. 

'As we enter the era of KRAS-targeted therapies, having a screening tool that tracks the same mutation becomes increasingly important,' said Chawla.

'That combination could fundamentally change how we identify high-risk patients, monitor microscopic disease, and potentially intervene earlier before recurrence becomes clinically visible, ultimately getting more patients to cure.'