You try one of the new blood-based tests for colon cancer, and unfortunately, the results come back “abnormal.”

Those are alarming findings, of course.  But for too many U.S. patients, no further steps are taken, a new study finds.

“Blood-based colorectal cancer screening is promising, but it only works if individuals complete the follow-up colonoscopy,” said study senior author Dr. Folasade May.

“More efforts are needed to help patients follow through to actually diagnose and treat the disease,” said May, an associate professor of medicine at the David Geffen School of Medicine at UCLA.

Colorectal cancer remains the second-leading cancer killer, with 52,900 related deaths expected during 2025, according to the American Cancer Society.

Luckily, there are ways to spot the disease early, when it is most preventable. 

These include colonoscopy (recommended start time is age 45 for people at average risk), stool-based tests, and, more recently, blood-based testing. 

The latter is a non-invasive, relatively easy means of cancer screening.

But how often do patients follow up and book an appointment for a colonoscopy (the gold standard for screening) if their blood test comes back “abnormal’?

To find out, May’s team looked at Medicare claims data for more than 6,000 people aged 45 and older who had taken a blood-based colorectal cancer screening test, called Shield (made by Guardant Health), between 2022 and 2024.

A total of 452 users received an abnormal result. Typically, these patients should book a colonoscopy within the next six months to ascertain whether they have a cancer. 

The study findings weren’t encouraging: Fewer than half (49%) of patients who received an abnormal result on their Shield test completed follow-up colonoscopy within six months, and that percentage only rose to 56% when the researchers extended follow-up to two years.  Rates didn't seem to vary based on race or ethnicity. 

The findings are about on par with follow-up rates for folks using stool-based tests, the researchers noted. 

People who were using Medicare Advantage programs were significantly less likely to go for follow-up colonoscopy than people with private insurance, the study found.

The bottom line, according to the researchers: “As blood-based colorectal cancer screening technologies become [U.S. Food and Drug Administration] FDA-approved and adopted by physicians and patients, we must prioritize strategies to ensure timely follow-up.”

The findings were published July 29 in the journal Gastroenterology.