Colorectal Cancer Blood Tests Show Promise, But Follow-Up Is Lacking

A study led by investigators at the UCLA Health Jonsson Comprehensive Cancer Center 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. Follow-up colonoscopy is a critical next step to confirm the presence of colorectal cancer or pre-cancer after an abnormal screening result. These follow-up rates are comparable to those observed with stool-based screening tests, but remain far below optimal levels needed for timely cancer detection and treatment.

The team also found that individuals with Medicare Advantage were significantly less likely to complete follow-up colonoscopy compared to those with private insurance, and that having fewer health conditions increased the likelihood of timely follow-up. Unlike prior studies of stool-based screening, race and ethnicity were not significant predictors of follow-up completion in this cohort.

Background

Colorectal cancer is the second leading cause of cancer-related deaths in the US among men and women combined, and regular screening can save lives by detecting it early. While traditional tests, such as colonoscopy or stool-based tests, are effective, many individuals do not get screened due to barriers such as fear, limited access, or challenges with test preparation. Blood-based screening tests offer a non-invasive, more convenient alternative for patients not amenable to the preferred colonoscopy or stool-based screening tests. However, to ensure these tests truly lower cancer rates and save lives, it is crucial to understand how often patients follow through with a colonoscopy, a key second step after an abnormal result.

Method

Researchers conducted a retrospective analysis using medical claims data from over 6,000 individuals aged 45 and older who received a blood-based colorectal cancer screening test, called Shield (Guardant Health), between 2022 and 2024. The study focused on the 452 individuals who received an abnormal result and examined how many completed a follow-up colonoscopy within six months.

Impact

This study provides important real-world data on follow-up colonoscopy rates after abnormal results from blood-based colorectal cancer screening. Timely follow-up is critical because it enables early detection and treatment of colorectal cancer.

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

Reference: Zaki TA, Zhang NJ, Forbes SP, Raymond VM, Das AK, May FP. Colonoscopic follow-up after abnormal blood-based colorectal cancer screening results. Gastroenterol. 2025;0(0). doi: 10.1053/j.gastro.2025.07.019

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