Blood tests for colorectal cancer screening are now within reach
Over the past several decades, a puzzling trend has emerged in colorectal cancer (CRC) statistics. While rates are falling among people over 65, they are climbing in younger adults, with the sharpest increase seen in those under 55. In 2019, adults 54 and younger accounted for about 20 percent of new CRC cases, up from 11 percent in 1995.
The question remains largely unanswered, but many experts point to the obesity epidemic as a major driver. Aasma Shaukat, a gastroenterologist and researcher at New York University Langone, explains that the generation now facing higher colon cancer rates grew up during the obesity epidemic. The long-term effects of obesity, metabolic syndrome, and diabetes may accelerate the pathway to colon cancer.
This rising incidence underscores the importance of CRC screening, though current methods suffer from low uptake. The gold standard remains the invasive colonoscopy. Other options include home-based stool tests like the fecal immunochemical test (FIT) and Cologuard, approved by the FDA in 2014. Yet nearly 40 percent of eligible adults aged 45 to 75 have not been screened with either method.
Many patients express dissatisfaction with the existing screening choices. They frequently report aversion to stool tests or to scheduling and undergoing a colonoscopy, leading to missed appointments or cancellations. As one patient put it, wouldn’t a blood test be easier?
A breakthrough is on the horizon: blood-based cancer detection, or liquid biopsies, could make screening easier and earlier. In 2024, the FDA approved Guardant Health’s Shield test as the first blood test to screen for CRC in adults 45 and older. Other companies are pursuing similar approaches, including Freenome, which submitted CRC blood test data to the FDA in 2024 with hopes for approval in 2026.
Although these early blood tests do not yet match the accuracy of colonoscopy, they offer a promising new option for CRC detection.
Regardless of the method, any screening is better than none, according to Shaukat.
How the Shield test works and what evidence shows
Guardant Health’s Shield test analyzes a person’s blood for fragments of tumor DNA circulating in the bloodstream (ctDNA) shed by a CRC tumor. The FDA approval relied on the ECLIPSE study, which enrolled more than 20,000 participants globally. Results published in The New England Journal of Medicine show the Shield test detected CRC in 83.1 percent of individuals with confirmed cancer, and correctly yielded a negative result in 89.9 percent of those without CRC. The test’s ability to detect precancerous lesions before cancer, however, was more limited, with only 13.2 percent of advanced precancerous lesions identified by blood tests.
In practice, Shield seems well-suited for people who already have a cancerous tumor but want to avoid colonoscopy. For detecting early-stage precancerous changes before cancer develops, the test still needs substantial improvements before it can serve as a reliable screening tool.
Adoption and access
Since its approval, Shield has been incorporated into the National Comprehensive Cancer Network’s CRC screening guidelines and is covered by Medicare. Guardant Health is coordinating with private payers and other organizations to expand access. In 2025, the company announced a partnership with PathGroup to offer Shield in more than 250 hospitals across 25 states.
Other players are moving quickly. Freenome has licensed technology to Exact Sciences to help bring their blood-based CRC test to market, with a projected FDA approval and launch in 2026. Freenome emphasizes base-pair resolution in its approach, aiming for stronger detection of early lesions.
Experts weigh the strengths and limits
Shaukat notes that Freenome’s and Guardant Health’s data still fall short of the ideal sensitivity for advanced adenomas, the most important precursors to cancer. She points out that current stool-based tests detect advanced adenomas at roughly 45 percent, and there is a clear call from clinicians for higher sensitivity in these new blood tests.
Nonetheless, leaders in the field remain optimistic. They view these tests as the first step in a broader evolution of cancer screening. Some colleagues speculate about convenient, clinic-based blood draws at hospitals or mobile clinics, with later access at standard labs for broader use.
The broader vision is compelling: one blood test today for multiple cancers tomorrow
Industry executives frame the technology as a stepping-stone toward multi-cancer screening from a single blood sample. Guardant Health and Freenome are both pursuing broader panels that could detect markers across several cancer types. Guardant’s Shield test was selected for inclusion in an National Cancer Institute study examining ten cancer types, alongside emerging techniques that target specific epigenetic markers. The FDA has granted Breakthrough Device designation to Guardant’s multi-cancer approach, signaling accelerated development.
As one executive puts it, the idea is the ultimate goal: one tube, one cancer today; one tube, multiple cancers tomorrow. The potential is large enough to reshape how we approach cancer detection, especially given the predicted growth of the liquid biopsy market into the late 2020s.
Practical takeaways for today
Right now, expanding access to blood-based CRC screening is moving ahead, and real-world data show strong engagement with the Shield test: early analyses indicate high screening completion rates among those offered the test. Other innovations—such as capsule-based colon screening—are being explored as alternatives to traditional colonoscopy, though current capsule technologies face practical limitations.
In the near term, blood-based CRC screening is unlikely to replace colonoscopy entirely, but it could complement existing options, particularly for people who haven’t engaged with screening programs. The overarching goal remains clear: increase overall screening uptake and catch cancers earlier when treatment is most effective. As Craig Eagle of Guardant Health puts it, this technology represents a meaningful shift in early detection, one that could dramatically alter the cancer landscape.
Would you consider a blood test for cancer screening if it could reduce the burden of traditional methods? Do you think this approach could reach the groups currently underscreened by colonoscopy and stool tests? Share your thoughts in the comments.
