American Cancer Society adds blood and stool tests to colorectal screening guideline

The American Cancer Society has updated its colorectal cancer screening guideline for the first time since 2018, formally incorporating a blood-based test and two newer stool-based tests in a bid to expand options and reach the roughly 1 in 3 eligible adults who remain unscreened.

The update, published in CA: A Cancer Journal for Clinicians late last month, says that average-risk adults should begin screening at age 45 and continue through 75 for those with a life expectancy of more than 10 years. What changed is the menu of recommended tests. The guideline now includes Guardant Health's Shield, an FDA-approved blood test that detects tumor DNA; Geneoscopy's ColoSense, an at-home multitarget stool RNA test; and Abbott's Cologuard Plus, a next-generation multitarget stool DNA test. Freenome's SimpleScreen blood test, still under FDA review at publication, was also evaluated.

To reach its conclusions, the ACS Guideline Development Group commissioned a targeted systematic evidence review assessing each test's diagnostic performance, then layered in published microsimulation modeling studies to project how the tests would affect colorectal cancer incidence and mortality at the population level. That two-part approach, clinical validation data plus modeling, is how the group weighed not just whether a test detects cancer, but whether adding it would plausibly save lives across a screened population.

The performance data drove a clear hierarchy. Stool-based tests and visual exams, particularly colonoscopy, remain the preferred options. In validation studies, ColoSense showed 94.4% sensitivity for colorectal cancer and 45.9% sensitivity for advanced adenomas, while Cologuard Plus demonstrated 93.9% sensitivity for cancer with improved specificity over the original Cologuard. Shield, by contrast, detected colorectal cancer with roughly 83% to 84% sensitivity but performed notably worse on precancerous lesions and stage I disease.

That gap is why the ACS recommends blood-based tests only for patients who decline or fail to complete a preferred test. Compared with established stool-based tests, blood-based tests demonstrated lower sensitivity for both advanced precancerous lesions and stage I cancers, with studies predicting less effectiveness in reducing colorectal cancer incidence and mortality. Stool tests are recommended every three years; a positive result on any noninvasive test requires follow-up colonoscopy, preferably within six months.

The logic for including a less sensitive test at all is adherence. "We need to increase our emphasis on colorectal cancer as a highly preventable disease as much as a treatable one," said Robert Smith, Ph.D., the report's senior author and ACS senior vice president for early cancer detection science in a news release. "By offering more screening tools in our guideline update, more eligible adults will be able to participate in lifesaving colorectal cancer testing." A test a patient will actually take, the reasoning goes, beats a superior test left undone.

For health plans, the equity and coverage implications are explicit. "Coverage and affordability remain among the biggest factors in whether eligible individuals get screened for colorectal cancer," said Lisa Lacasse, president of the ACS Cancer Action Network, which said it will keep pressing for policies that eliminate out-of-pocket costs.

Colorectal cancer incidence and mortality rates have steadily declined in the United States over the past several decades, which Smith and his colleagues wrote can be largely attributable to improvements in screening, early detection and treatment. However, overall declines in incidence obscure increasing rates from 2013 to 2022 in those younger than 50 years (3% increase per year) and aged 50–64 years (0.4% increase per year), largely because of increasing numbers of distal colon and rectal tumors. They note that after decades of decline, rectal cancer incidence increased by 1% per year from 2018 to 2022, now accounting for nearly a third of all colorectal cases. Among U.S. adults younger than 50, colorectal cancer is now the leading cause of cancer death among men and the second leading cause among women

Smith and his colleagues wrote in CA that the rising incidence of colorectal cancer in the younger population appears to have a number of causes, including perinatal and early life exposures, diet, exercise, tobacco and alcohol use, antibiotic exposures, and metabolic syndrome. Among US adults younger than 50 years, CRC is now the leading cause of cancer death among men and the second leading cause among women.