Blood Test Increases Colorectal Cancer Screening in Persons Who Declined Colonoscopy and Fecal Immunochemical Test: A Randomized Controlled Trial

The septin 9 blood test is indicated for colorectal cancer screening in individuals who decline first-line tests, but participation in this context is unclear. We conducted a randomized controlled trial to compare reoffering colonoscopy and fecal immunochemical test (FIT) alone versus also offering the blood test among individuals who declined colonoscopy and FIT.

Screen-eligible Veterans aged 50-75 years who declined colonoscopy and FIT within the previous 6 months were randomized to letter and telephone outreach to reoffer screening with colonoscopy/FIT only (control), or additionally offering the blood test as a second-line option (intervention). The primary outcome was completion of any screening test within 6 months. The secondary outcome was completion of a full screening strategy within 6 months, including colonoscopy for those with a positive noninvasive test.

Of 359 participants who completed follow-up, 9.6% in the control group and 17.1% in the intervention group completed any screening (7.5% difference; P = .035). Uptake of colonoscopy and FIT was similar in the 2 groups. The full screening strategy was completed in 9.0% and 14.9% in the control and intervention groups, respectively (5.9% difference; P = .084).

Among individuals who previously declined colonoscopy and FIT, offering a blood test as a secondary option increased screening by 7.5% without decreasing uptake of first-line screening options. However, completion of a full screening strategy did not increase. These findings indicate that a blood test is a promising method to improve colorectal cancer screening, but obtaining a timely colonoscopy after a positive noninvasive test remains a challenge (ClincialTrials.gov number, NCT03598166).