Background: Average-risk screening for colorectal cancer (CRC) is effective and recommended. The U.S. Preventive Services Task Force issued grade A and B recommendations for screening ages 50-75 and 45-49, respectively, however the recommendation for the older population (ages 76-85) is grade C (moderate certainty that the net benefit is small). With emerging blood-based CRC screening, we evaluated the benefits of screening the older population with continued multi-target stool DNA (mt-sDNA) or FIT strategies and/or with a modality shift to blood-based tests after age 75. Methods: Using the validated CRC-AIM microsimulation model, triennial mt-sDNA and annual FIT screening (ages 45-75) followed by four strategies for ages 76-85 (no screening, continued mt-sDNA/FIT, or a modality shift to blood-based screening using either CMS criteria [CMS] or recently reported blood test data from the ECLIPSE study¹ [BT; Guardant Health, Inc.] were considered. For CMS criteria and BT, CRC sensitivity were set at 74% and 83%; and adenoma sensitivity was set to 20%, and 13%; and CRC specificity was set to 90% for both tests. Real-world (RWE) adherence for initial screening was set to 80% (CMS, BT), 65.6% (mt-sDNA), and 42.6% (FIT). Adherence for follow-up colonoscopy was set to 72.1% (mt-sDNA, CMS, BT) and 46.0% (FIT). Results: Screening among the population aged 45-85 resulted in 281 life years gained (LYG) with continued mt-sDNA as compared to 193 with continued FIT. Furthermore, mt-sDNA reduced CRC mortality by 70% as compared to 49% by FIT (Table). When screening modality was shifted to CMS (76-85 year olds), mt-sDNA/CMS resulted in 279 LYG as compared to 196 for FIT/CMS. CRC incidence was reduced by 59% (mt-sDNA/CMS) as compared to 38% (FIT/CMS), and mortality declined by 69% (mt-sDNA/CMS) as compared to 51% (FIT/CMS). Reductions in disease burden were lower when modality was switched to BT after age 75 due to reduced test performance. Conclusions: Extending CRC screening to the older population with continued mt-sDNA demonstrated the best health outcomes compared to other modalities. A modality shift after age 75 to blood-based testing resulted in greater LYG as compared to no screening, with performance at CMS criteria yielding better results than BT. Therefore, despite inferior performance, blood-based tests may offer a CRC screening option for older patients who are unable to complete stool testing.

LYG: life-years gained; COL: colonoscopy; CMS Blood: Center for Medicare Services recommended blood-test; BT: trial performance blood-based test. *Per 1000 individuals ¹ECLIPSE study.