A Simple Blood Test Can Now Screen for Colon Cancer
One in five people diagnosed with colon cancer right now is under 55. That number has been climbing for years and nobody has a clean explanation for why. What the American Cancer Society is doing about it — as of Wednesday — is giving people one more way to get screened that doesn't involve a colonoscopy.
The new guidelines add a blood test called Shield, made by Guardant Health, to the official list of recommended colorectal cancer screening options. It's a simple blood draw at your doctor's office. No prep. No procedure. No day off work. The FDA approved it in 2024 and a clinical trial published in the New England Journal of Medicine found it detected 83% of the cancers that colonoscopy found.
That number — 83% — is the one that matters. It's not as good as a colonoscopy. The American Cancer Society is upfront about that. Colonoscopies are still the gold standard and blood tests should come second, not first. If you get the blood test and something looks abnormal you still need a colonoscopy to follow up.
But 83% of something is a lot better than 0% of nothing. And for millions of people, the choice has effectively been between a colonoscopy they keep avoiding and no screening at all.
Why People Skip Screening in the First Place
The prep for a colonoscopy is genuinely unpleasant. The procedure requires sedation. You need someone to drive you. You lose most of a day. For people without good insurance, flexible jobs, or easy access to a gastroenterologist it's even harder to make happen. Add general anxiety about what might be found and a lot of people just keep putting it off.
That's the gap the American Cancer Society is trying to close. The updated guidelines also include a new at-home stool test option that detects hidden blood and molecular markers — another lower-barrier alternative for people who won't get a colonoscopy.
"No matter which test you choose, what's most important is to get screened," said Dr. William Dahut, chief scientific officer at the American Cancer Society. The organization specifically called out underserved, rural, and minority populations who have historically had lower screening rates and worse outcomes as a result.
The Young People Problem
Overall colorectal cancer rates have actually gone down over the last decade — largely because colonoscopy screening has gotten more common in older adults. But in people under 50 rates have been climbing about 2% every year. The American Cancer Society lowered its recommended screening age from 50 to 45 a few years ago because of this trend.
Colon cancer is the third most common cancer in the world. It's also one of the most preventable. The genuinely frustrating part is that it rarely causes symptoms until it's already spread — which means by the time someone notices rectal bleeding, unexplained weight loss, changes in bowel habits, or unusual cramping, the disease may already be more advanced than it needed to be.
Catch it early and the outcomes are dramatically better. That's the whole argument for screening — and now there are more ways to do it than there used to be.
If you're 45 or older and you've been putting off getting screened, this is a pretty direct sign to stop waiting.
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