MW A new blood test can help detect colon cancer, but it's not as good as the test you hate to take
By Jaimy Lee
The symptoms of colon cancer are often silent, and colonoscopies can prevent and detect colon cancer
The American Cancer Society recently recommended that two blood tests can be an option for people who won't get a colonoscopy or do a stool test.
No one looks forward to a colonoscopy, but for the millions of Americans who refuse screening, a simple blood test could help catch colon cancer.
For the first time, the American Cancer Society recommended in an announcement last month that a blood test could be used to screen people who choose not to or can't get a colonoscopy.
However, the test is far less effective than a colonoscopy, which is the gold standard in preventing and detecting colon cancer, or a stool test, which was made popular over the past decade by the humorous ad blitz created by Exact Sciences, the developer of the Cologuard stool test.
"All of us agree that a screening test, any screening test, is better than no screening test," said Trisha Pasricha, a gastroenterologist and director of the Institute for Gut-Brain Research at Beth Israel Deaconess Medical Center in Boston. "If that's the only option, of course we want you to get it done because at least it gives us some helpful information that we can act on."
Millions of Americans are skipping their colonoscopies due to concerns about the cost, time commitment and undergoing a procedure with anesthesia. But the data surrounding colon-cancer rates is alarming, and getting screened is crucial to preventing colon cancer or catching it at an early stage.
Even though colon cancer in the overall U.S. population has declined in recent decades, it is now the leading cause of cancer deaths in people under the age of 50. It's also the third-most-common cancer in the U.S., excluding skin cancers. Back in 2018, the ACS lowered the starting age for screening to 45, down from 50, to deal with the sharp uptick of diagnoses in younger people.
Getting roughly 150 million Americans to complete screening is still a problem. About 40% of eligible people either get a colonoscopy every 10 years or do a stool test every three years, per the guidelines. Another 30% have done some screening. That leaves 30% of eligible adults who aren't being screened at all for a cancer that often doesn't have symptoms until it's more advanced .
"We've got 50 million people out there who aren't doing anything," said Michael Weisberg, a recently retired gastroenterologist in Texas, "and we have a disease that affects 4% to 6% of Americans in their lifetime."
The good news is that there is now a wider range of testing options to ensure that more Americans are getting tested for colon cancer. But some doctors worry that people will seek out the less-sensitive blood tests to avoid a stool test or colonoscopy without understanding that those tests are far less effective at detecting cancer and the worrisome polyps that could turn into cancer.
"The blood test is not a shortcut for the average person," Pasricha said. "Don't think of the blood test as an easy way out."
Colon-cancer rates are rising
There is no single reason why colon-cancer rates have been rising in people younger than 50, but it's likely driven by increasingly unhealthy diets that lack fiber and over-index on ultraprocessed foods. A study published last year found that exposure in childhood to colibactin, a bacterial toxin that comes from certain E. coli strains and can change the DNA in colon cells, may be one cause for early-onset colon cancer.
"The way that we're eating in our childhood has dramatically shifted from the way our parents and grandparents were eating," Pasricha said. "A lot of it is, ultimately, coming down to the ultraprocessed foods, the sugary beverages, the lack of fiber in our diets - all of these things play a role."
One of the challenges with the current screening recommendations is that the average person should start getting screened at age 45, for at least the next 30 years. That means people under the age of 45 who are being diagnosed with colon cancer are doing so only when they present with symptoms like rectal bleeding or extreme weight loss.
"I would not be surprised if over the next couple of years it goes from 45 to 40," said Marc Fenster, a gastroenterologist at Episcopal Health Services in Queens, N.Y., about the recommended age to start screening.
Even though the federal government mandates coverage of preventive colonoscopies and stool tests at no cost to the patient, money can still be a reason why people put off getting screened. If someone is younger than 45, their health insurance might not cover the procedure. And if they are getting screened because of symptoms or a family history, it's no longer considered a preventive test.
Worrying about costs is one explanation why people don't get screened for colon cancer, but there are several other reasons why someone may avoid getting a colonoscopy or doing a stool test.
Sometimes, they can't take the time off work to do the prep for a colonoscopy, which includes taking laxatives to clean out the bowels, or the procedure itself, which requires sedation and a friend or family member picking them up. In other cases, people don't have reliable housing to get a stool test mailed to. Others worry about the invasiveness of a colonoscopy and undergoing anesthesia or are too sick with a chronic disease to be sedated. Some people are just embarrassed about the overall process.
How the tests work
There are three ways to look for colon cancer and polyps located in the intestinal lining. About 5% to 10% of polyps, which most people will have at some point in their lives, become cancerous, according to Pasricha. If a stool or blood test comes back positive, the recommendations say those patients should then undergo a colonoscopy.
That's why the gold standard is a colonoscopy, a minimally invasive procedure that uses a scope with a camera to examine the large intestine's lining for precancerous or cancerous polyps. Though time-consuming, it can detect 95% of cancers and a similar percentage of high-risk polyps. During the procedure, physicians will remove any polyps of concern.
"The reason why colon cancer is a preventable cancer is because it starts off as a polyp in the overwhelming majority of cases, which is a harmless tissue but which can have the genetic factors to eventually grow and eventually turn it into cancer," Weisberg said.
Then, there are several stool tests, which includes Abbott's $(ABT)$ Cologuard products and Geneoscopy's ColoSense. With those tests, a patient takes a stool sample at home and mails it back to the company for testing. The Cologuard Plus test, which was approved last year, catches about 95% of cancer and 43% of high-risk polyps.
And now there is a blood test: Guardant Health's (GH) Shield test, which is done with a standard blood draw. It's easy but far less effective at detecting colon cancer, catching about 83% of cancers and only 13% of high-risk polyps. It was approved in 2024 and isn't uniformly covered by health insurance at this time. Another blood test called SimpleScreen is currently under review at the Food and Drug Administration, and a decision is expected imminently.
People who get a positive stool or blood test should then undergo a colonoscopy.
For the Americans thinking 83% sounds like a good-enough option to avoid a colonoscopy or a stool test, think again. The American Cancer Society characterizes the test as a kind of last resort for people who opt out of other types of tests, saying it's not a "preferred" test and "should be recommended only to individuals who decline or have not completed" another form of screening.
"These tests are all good to have in our back pocket and all good to be able to offer to patients," Fenster said, "but patients should understand that they're not the same as a colonoscopy."
-Jaimy Lee
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(END) Dow Jones Newswires
June 04, 2026 15:39 ET (19:39 GMT)
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