The American Cancer Society updated its colorectal cancer screening guidelines May 27 to include new blood- and stool-based screening options, while making clear that the blood-based test is a last resort, not a replacement for more sensitive alternatives.
Here are five things to know:
1. The updated ACS guidelines added the Guardant Health blood test Shield to the list of recommended colorectal cancer screening options, but with a significant caveat. ACS recommended the blood-based test Shield only for individuals who decline or do not complete preferred screening tests, noting that blood-based tests demonstrated lower sensitivity for advanced precancerous lesions and stage I cancers compared with established stool-based tests.
2. The updated guidance added two stool-based screening options that detect hidden blood and molecular markers: next-generation multitarget stool DNA test Cologuard and the multitarget stool RNA test ColoSense. ACS recommended both every three years.
Cologuard has been available since 2014 and is already well known to GI practices. ColoSense is newer. Both were positioned above Shield in the updated guidelines, which is a signal that stool-based alternatives are considered more clinically reliable than blood-based testing at this stage of the evidence base.
3. More than 20 million Americans eligible for colorectal cancer screening have not been tested as recommended, representing about 1 in 3 adults, according to ACS. That gap, rather than clinical preference, is the primary argument for blood and stool alternatives to colonoscopy. The less invasive the test, the more likely a hesitant patient gets screened at all.
ACS also cited research showing colorectal cancer is now the top cancer killer of adults under age 50 — the same early-onset trend driving increased colonoscopy and endoscopy demand across GI practices.
4. The guidelines reaffirmed that average-risk adults should begin screening at age 45 and continue through age 75 for those with a life expectancy greater than 10 years. They did not change colonoscopy’s recommended interval or its position as the most clinically comprehensive screening option.
Shield detected 83% of colorectal cancers in studies but only 13% of dangerous precancerous polyps. Colonoscopies find approximately 95% of those polyps. The ACS guidelines reflect that gap — stool-based tests perform better than blood-based tests on advanced precancerous lesion detection, and colonoscopy remains the only option that both detects and removes polyps in a single procedure.
5. The ACS guidelines update gives blood- and stool-based tests formal clinical standing, but coverage remains inconsistent. Shield meets these performance requirements for Medicare coverage and is the first and only blood test to meet the threshold with 83% sensitivity and FDA approval. As such, Shield is covered by Medicare with no co-pay for most beneficiaries, while commercial coverage varies.
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