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A simple blood test can detect eight different types of cancer. It does this by detecting the various sizes of tumour DNA fragments that flow through the body.
At the moment, most cancer screening tools are limited to specific areas of the body – for example, mammograms for spotting breast cancer and faecal tests for detecting bowel cancer. Whole-body MRI and CT scans can identify tumours throughout the body, but only once they have grown large enough to see.
As a result, many research groups are working on developing blood tests that can detect multiple different cancer types while they are still in early, treatable stages.
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A popular approach is to genetically sequence blood to see if it contains any tell-tale tumour DNA markers. But this is like looking for needles in a haystack because of the large volume of non-cancerous DNA that also circulates in the blood.
Now, Florent Mouliere at Cambridge University and his colleagues have devised a different approach that doesn’t require time-consuming genetic sequencing and is potentially more accurate.
Size matters
They discovered that DNA fragments leaked by tumours often have different sizes to non-cancerous DNA fragments in the blood. For example, DNA fragments shed by breast, bowel and ovary cancers tend to be shorter.
By looking for characteristic tumour DNA fragment sizes in blood samples, the researchers were able to detect 94 per cent of breast, bowel, ovary, skin, and bile duct cancers in 68 cancer patients, with a false positive rate of 2.5 per cent, i.e., the rate at which it identified a cancer that wasn’t really there. They were also able to identify 65 per cent of pancreas, kidney, and brain cancers in another 57 patients.
In comparison, an existing blood test called CancerSEEK that looks for genetic and protein tumour markers in the blood was found to detect 70 per cent of common cancers on average. However, CancerSEEK was tested on earlier-stage cancers which probably made detection harder, says Mouliere.
In theory, the new test could be used to detect all kinds of tumours, says Mouliere. It’s simple enough for any commercial lab to do, meaning it could become available to the public in the near future, he says.
Journal reference: Science Translational Medicine, DOI: 10.1126/scitranslmed.aat4921
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