The American Cancer Society has released its first major update to colorectal cancer screening guidelines since 2018. The revision follows the approval of new molecular-based screening tests by the FDA and ongoing concerns about rising colorectal cancer rates among younger adults. Researchers have linked factors such as diet and environmental exposures to the increase in early-onset cases.
Blood-based tests, also known as liquid biopsies, are not recommended as preferred screening options at this time. The ACS advises that these tests should only be offered to individuals who decline or have not completed a preferred screening test. The main issue is sensitivity. Blood-based tests showed lower sensitivity for advanced precancerous lesions and stage I cancers compared with stool-based tests. This matters because the main goal of screening is to prevent cancer by finding and removing precancerous growths. One modeling study estimated that 80% of the long-term benefit from screening comes from detecting these lesions. Blood-based tests had very low sensitivity for advanced precancerous lesions, around 13% in two large studies. Specificity also declines with age, dropping from above 90% in people younger than 55 to about 80% in those 70 and older, leading to more false positives. The ACS acknowledges that blood-based tests have value for people who would otherwise not get screened at all.
Two new stool-based tests have been added to the ACS list of preferred screening options. ColoSense uses an algorithm that combines eight RNA biomarkers, a fecal immunochemical test, and self-reported smoking status. In a validation study, it showed 94.4% sensitivity for colorectal cancer, 100% sensitivity for stage I disease, and 45.9% sensitivity for advanced adenoma. It received FDA approval in 2024. Cologuard Plus is an updated version of the original Cologuard test with a revised marker set. In the BLUE-C study, it showed 93.9% sensitivity for colorectal cancer and 43.4% sensitivity for advanced precancerous lesions, with improved specificity. It also received FDA approval in 2024. Both tests are done every three years. Medicare and Medicaid coverage for ColoSense was still pending at the time of the guideline update.
A positive result on any non-colonoscopy screening test requires a follow-up colonoscopy, preferably within six months. The guidelines state that repeating a stool or blood test after a positive result is not acceptable. Real-world data show this is a problem. One randomized trial cited in the guidelines found that only 50% of participants with a positive blood-based test completed a follow-up colonoscopy within six months, compared with 70% of those with a positive fecal test.
The ACS reaffirmed its recommendation to start screening at age 45 for average-risk adults. Colorectal cancer incidence increased in adults under 50 at a rate of 3% per year between 2013 and 2022. Among U.S. adults under 50, colorectal cancer is now the leading cause of cancer death among men and the second leading cause among women. Despite the 2018 recommendation, only 37% of adults aged 45 to 49 reported being up to date with screening in 2023. Screening rates were lower among Hispanic, Asian, and American Indian or Alaska Native individuals compared with White and Black individuals.
Disparities in colorectal cancer burden remain serious. Age-adjusted incidence rates are 11% higher among Black individuals, and mortality rates are about 40% higher than White individuals. American Indian and Alaska Native populations have incidence rates 48% higher and mortality rates about 44% higher than White populations. Alaska Native people have more than double the incidence and mortality rates observed among White populations. Lack of insurance and lower socioeconomic status are linked to lower screening rates. The guidelines note that the anticipated high cost of newer tests will be a barrier for uninsured and underinsured populations. Annual high-sensitivity stool blood tests and older DNA stool tests remain the low-cost options. Modifiable lifestyle factors such as alcohol consumption also contribute to colorectal cancer risk.
