New blood test that shows 83% accuracy in detecting colon cancer could boost screening

Clinical study of a blood test shows 83% accuracy for detecting colorectal cancer
Clinical study of a blood test shows 83% accuracy for detecting colorectal cancer Copyright Canva
Copyright Canva
By Oceane Duboust
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A promising study showed that a blood test diagnosed colorectal cancer with an 83 per cent accuracy, giving an alternative to current stool tests.


Researchers have developed a test that could detect colorectal cancer with 83 per cent accuracy using a simple blood sample, according to a new study.

The blood test’s high accuracy is comparable to current at-home stool tests.

The team published their findings in the New England Journal of Medicine.

“The results of the study are a promising step toward developing more convenient tools to detect colorectal cancer early while it is more easily treated,” William M Grady, a gastroenterologist at Fred Hutchinson Cancer Center based in Seattle in the US, said in a statement.

“The test, which has an accuracy rate for colon cancer detection similar to stool tests used for early detection of cancer, could offer an alternative for patients who may otherwise decline current screening options," he added.

Stool tests are the currently used diagnostic tool and detect blood or damaged DNA in the samples. Other options include sigmoidoscopy and colonoscopy, which involve inserting a tube into the rectum and the colon.

Colonoscopy is considered the “gold standard” for screening. CT colonography, also called virtual colonoscopy, uses X-rays to detect cancer’s signs.

The test developed by researchers detects in the blood circulating tumour DNA (ctDNA), DNA that is shed by the cancerous cells.

It was tried on nearly 8,000 people between 45 and 84 who also underwent standard colonoscopy with researchers then comparing the outcomes.

The blood test confirmed 83.1 per cent of participants diagnosed with colorectal cancer while 16.9 per cent got a negative result with the ctDNA technique but were positive using colonoscopy.

The test showed higher sensitivity towards detecting colorectal cancers, even in their early stages, but exhibited lower sensitivity in identifying advanced precancerous lesions that have the potential to develop into cancer over time.

Second deadliest cancer

Europe has one of the highest incidence rates for colorectal cancer.

In the EU, it was the second most frequent cancer after breast cancer, representing 12.7 per cent of the new cancer diagnoses in 2020 and the second cause of cancer-related deaths.

Screening is recommended for adults aged between 50 and 69 who have an average risk or not known to have an elevated risk due to different factors, according to European Commission guidance.

However, there is an heterogeneity among European countries. In just over half of the EU member states, the majority of the population aged 50–74 years had never been screened for colorectal cancer in 2021, according to Eurostat.

Finland, the Netherlands, and Denmark had screening rates above 60 per cent while Serbia, Montenegro, and Hungary had rates below 10 per cent.

“Getting people to be screened for cancer works best when we offer them screening options and then let them choose what works best for them,” said Grady.

The earlier the diagnosis is, the higher the survival rate is. Screening tests can find precancerous polyps, allowing them to be removed before they turn into cancer, according to the US Centers for Disease Control and Prevention (CDC).


An early diagnosis leads to a survival rate superior to 90 per cent. However, when the cancer metastases, or migrates, to other body parts, this rate falls to 25 per cent.

“We continue to see younger people getting colorectal cancer and it’s now the third most common cancer for people under the age of 50,” Grady said. “Having a blood-based test for people to take during routine doctor’s visits could be an opportunity to help more people be screened,” he added.

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