Blood Tests Show Potential for Colorectal Cancer Detection

Colorectal cancer remains the second leading cause of cancer-related deaths in the United States, yet many individuals miss screening due to fear, limited access, or the burdens of test preparation. Early detection through regular screening is critical to reducing mortality. Traditional screening methods such as colonoscopies and stool-based tests, though effective, are often underutilized.

Blood-based screening offers a convenient, non-invasive alternative, especially for patients unwilling or unable to undergo more invasive procedures. However, for these tests to be effective in lowering cancer rates, they must be followed by diagnostic confirmation. Now, a study has revealed that colonoscopy rates after abnormal blood-based screening results mirror those for stool-based tests, but timely follow-up still remains a challenge.

The study, led by researchers from the UCLA Health Jonsson Comprehensive Cancer Center (Los Angeles, CA, USA), evaluated Shield, a blood-based colorectal cancer screening test developed by Guardant Health (Palo Alto, CA, USA). The team conducted a retrospective analysis using medical claims data from more than 6,000 individuals aged 45 and older who underwent screening with Shield between 2022 and 2024. Their analysis focused on the 452 individuals who received abnormal results and assessed the proportion who went on to complete a colonoscopy within six months.

The study found that while blood-based tests offer a more convenient option for colorectal cancer screening, only 49% of patients completed a follow-up colonoscopy within six months, and just 56% did so at any point during the two-year study period. A further examination of demographic and insurance-related factors revealed that patients enrolled in Medicare Advantage were significantly less likely to pursue follow-up compared to those with private insurance, while individuals with fewer preexisting health conditions were more likely to complete timely follow-up.

Interestingly, unlike with stool-based screening tests, race and ethnicity did not significantly influence follow-up completion. The study’s findings, published in Gastroenterology, offer important real-world insights into the implementation of blood-based colorectal cancer screening. The results underscore the urgent need for strategies that promote timely diagnostic colonoscopies following abnormal screenings. Without this critical second step, the promise of blood-based testing to save lives remains limited. Researchers emphasize that efforts should focus on patient education, system-level interventions, and policy changes to improve compliance with follow-up protocols and fully realize the benefits of this innovative approach.

“Blood-based colorectal cancer screening is promising, but it only works if individuals complete the follow-up colonoscopy. More efforts are needed to help patients follow through to actually diagnose and treat the disease,” said Dr. Folasade May, senior author of the study.

Related Links:
UCLA Health Jonsson Comprehensive Cancer Center
Guardant Health