Researchers from Johns Hopkins University, Baltimore have published a single blood test, CancerSEEK, that can detect the presence of eight cancers by analysing mutations in cell free DNA and levels of circulating proteins. This potentially heralds a breakthrough in the early detection of cancer although the test requires further testing in a population who have not already had their cancer detected clinically. This is particularly exciting for cancers like pancreas, liver and ovary which are difficult to detect and for which there are no screening tests available. The test has a very high specificity of greater than 99%, which should minimize false positives, and an average sensitivity of 70% although this may reduce to ~50% for the detection of very early stage cancers.
Prof Richard Marais, from Cancer Research UK, said it would take time to prove that it worked as an early diagnosis for cancer - at least five to six years. "Detecting cancer early, before the disease has spread is one of the most powerful ways to improve cancer survival and this interesting research is a step towards being able to do this earlier than is currently possible."
Paul Pharoah, professor of cancer epidemiology at the University of Cambridge, said more work was needed to assess how the test performs when cancers are less advanced. He 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 1 cancers in the study was only 40%."
And Dr Mangesh Thorat from the Centre for Cancer Prevention, Queen Mary University of London, said it looked promising "but with several caveats", "A significant amount of further research is needed before we can even contemplate how this might play out in screening settings," he said. "This is only a case-control study, and therefore needs further evaluation in large cohorts more representative of general population where such screening might be introduced."
The cost of CancerSEEK is less than $500 (£360) per patient, which is around the same price as a colonoscopy.
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