Improving screening rates could help catch cancer early and save lives, he said.
More than three-quarters of colorectal cancer-related deaths occur in people who are not up to date with screening.
However, a blood test isnt a substitute for a colonoscopy.
Photo Illustration by Michela Buttignol for Verywell Health; Getty Images
The best screening test is the one that gets done.
How Does the Shield Test Detect Colorectal Cancer?
Most people can get the Shield test during a routine annual physical.
People don’t need to change their diet or prepare in any special way before the blood draw.
People with colorectal cancer tend to have a higher concentration of those circulating DNA fragments.
There are also differences in the way DNA is expressed in colorectal cancer cells compared to normal cells.
Cologuard, a non-invasive test that gained FDA approval a decade ago, works in a similar way.
It analyzes stool samples for signs of blood and DNA fragments that may have come from cancer cells.
Stool passes right through the colon and rectum.
Thats like finding a needle in a haystack, Eagle said.
When cancer lesions are big, they shed more cells than those that are less developed.
That means a blood test is more likely to pick up signs of advanced cancers than early-stage disease.
How Accurate Is the Blood Test?
Guardant tested Shield in a randomized control trial of nearly 8,000 people.
About 83% of the 65 people who had colorectal cancer got a positive result on the Shield test.
The test missed 17% of those cases.
It picked up 55% of the stage 1 cancers.
Colorectal cancer often develops when noncancerous tumors, called adenomas, grow and become cancerous.
In the clinical trial, the Shield test detected about 13% of advanced adenomas.
What Are the Chances of False Positives?
In the clinical trial, about 0.4% of participants had confirmed colorectal cancer.
False positives can cause people to worry and spend money on follow-up exams they don’t necessarily need.
False positives were more common in older adults than in young adults.
That can help remove early-stage cancer growths and polyps that could turn into cancer.
Even the average risk individual has a 1 in 20 chance of developing colon cancer in their lifetime.
Its not really a low risk, Lieberman said.
What This Means For You
TheU.S.
The regularity varies from every year for a stool-based FIT test to every 10 years for a colonoscopy.
Some factors like medical conditions and age may influence which test is best for you.
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