S560 Adenoma Detection Rates From a Large Clinical Validation Study of a Blood-Based Colorectal Cancer Screening Test

Introduction: Colorectal cancer (CRC) is the second most common cause of cancer deaths in the United States. Colonoscopy can reduce CRC mortality by enabling earlier cancer detection or by removing cancer precursors. Higher adenoma detection rates (ADRs) have been associated with lower CRC mortality. ADR is a leading colonoscopy quality indicator, but ADR data for adults aged 45-49 yrs are limited. This study evaluates ADRs by age for a large real-world cohort of average-risk adults against the 2024 colonoscopy quality guidelines by the American College of Gastroenterology (ACG) and the American Society for Gastrointestinal Endoscopy (ASGE), providing robust, generalizable estimates for the CRC screening population. Methods: PREEMPT CRC was an observational, prospective clinical validation study of a blood-based test for CRC screening among asymptomatic, average-risk adults aged 45-85 years. The study included 201 diverse sites across the U.S. and abroad, with screening colonoscopies conducted by more than 5,000 endoscopists. Based on a thorough medical review of colonoscopy and pathology reports, ADRs were calculated across 27,010 subjects who completed screening colonoscopy, and compared to other studies and the ADR performance target of 35% overall, with 40% in men and 30% in women. Overall and sex-stratified ADRs were also calculated across 5-year age brackets. Results: The overall ADR for 45-85 yrs was 36.4% (35.8%, 37.0%). A significant difference (P < 0.0001) was observed between male subjects (43.5%, 42.6%-44.4%) and female subjects (30.8%, 30.0%-31.5%) across all age brackets. ADRs generally increased with age, with the steepest increase from 45-59 yrs. The ADR for 45-49 yrs (28.1%, 26.5%-29.8%) was consistent with 2 recent studies (Shaukat 2022, Bilal 2022) but below ADR performance targets, whereas the ADRs for 50-54 yrs (34.4%, 33.4%-35.5%) and 50-75 yrs (37.3%, 36.7%-37.9%) were at or above ADR performance targets. These observations held true when stratifying ADR by sex. Conclusion: ADRs for 45-85 yrs in PREEMPT CRC were above overall and sex-specific ADR performance targets. Despite lower ADRs for 45-49 yrs, adenomas were still detected in more than 1 in 4 screening colonoscopies among this age group, whose screening adherence is generally poor. This key finding underscores the benefit of initiating screening at 45 yrs and improving screening adherence in this age group to help reduce CRC incidence and mortality in subsequent decades.