Cancer breakthrough could pave the way for a universal blood test

Researchers have taken a step towards developing a universal blood test for cancer – one that can detect the devastating disease early and effectively.

Called CancerSEEK, the test, devised at Johns Hopkins University in Baltimore, has the potential to spot eight of the most common forms of the disease far earlier, giving patients a better chance of beating the disease. 

Catching cancers early – before they have spread to other regions of the body, known as metastasizing – is one of the key ways to reducing the risk of dying from them.

 In more than 1,000 patients, CancerSEEK detected cancer with 69% to 98% success rate (depending on cancer type) for five of eight cancer types. 

Ovarian cancer was the easiest to detect, followed by liver, stomach, pancreas, oesophageal, colorectal, lung and breast cancers, according to the study in Science. The success rate was much lower in stage I cancers, though, at 40%. 

Cancer tumours release tiny traces of mutated DNA and proteins into a person’s bloodstream. The team at John Hopkins initially studied several hundred genes and 40 protein markers, whittling the number down to segments of 16 genes and eight proteins. They could then study these genes and markers for signs of cancer at a much earlier stage, and for much less than current methods. 

The team studied 1,005 patients who had been diagnosed with stage I to III cancers, as well as 850 healthy control individuals. In some cases, the test was 99% specific, meaning that the likelihood of a healthy individual receiving a false positive result was extremely low.

In other cases, the test also gave information about the tissue that the cancer had originated from – a feat the team said has been difficult in past. This accuracy is part of CancerSEEK’s success, and uniqueness. 

“The ultimate goal of CancerSEEK is to detect cancer even earlier – before the disease is symptomatic,” the team said. The researchers estimate that the cost of this single blood test for eight cancer types may be less than $500, which is comparable to or lower than current screening tests for single cancer types.

“This field of early detection is critical, and the results are very exciting,” said Dr Cristian Tomasetti of Johns Hopkins University School of Medicine. “I think this can have an enormous impact on cancer mortality.”

However, there have been questions raised about how successful the test is at detecting cancers when the disease is far less advanced. Each cancer patient in the study had already been diagnosed. It is unclear how well this test works on people without any prior diagnosis. 

Speaking to the BBC, Paul Pharoah, professor of cancer epidemiology at the University of Cambridge, said: “Demonstrating that a test can detect advanced cancers does not mean that the test will be useful in detecting early-stage symptomatic cancer, much less pre-symptomatic cancer. The sensitivity for the stage I cancers in the study was only 40%.”

Image: Wikimedia Commons/Elizabeth Cook/Kaitlin Lindsay/John Hopkins Medicine/Science