Abstract 5108: Screening colonoscopy yields among adults aged 40 to 49 years after new screening guidelines

Abstract Objective: To analyze screening colonoscopy yields among adults aged 40 to 49 years since China Guideline for the Screening, Early Detection and Early Treatment of colorectal cancer (2020, Beijing) expanded the screening initiation age to 40, thus providing evidence to support lowering the screening initiation age to 40. Method: This population-based cross-sectional study was part of the framework of the Cancer Screening Program initiated by the Chinese government. We included residents aged 40-59 who underwent their first screening colonoscopy in 2020-2024. The study outcomes included: colorectal cancer (colon or rectal adenocarcinoma); advanced lesions (at least one adenoma ≥10mm or at least one adenoma with villous components or high-grade dysplasia); and other benign lesions. Robust Poisson regression was used to estimate the adjusted risk ratios (aRRs) for outcomes between age groups, with 50- to 59-year-olds serving as the reference group. Regression models were adjusted for region, sex, comorbidities, body mass index (BMI), and tobacco smoking history. Result: A total of 5040 eligible patients underwent a screening colonoscopy in 2020-2024, including 1529 aged 40-49 and 3511 aged 50-59. Females comprised 60.5% of the overall cohort, 53.7% had comorbidity, 23.7% had a history of tobacco smoking, and 39.7% had body mass index=24 (calculated as weight in kilograms divided by height in meters squared). Screening colonoscopy outcomes were generally slightly less frequent among the younger group compared with the older group, only the aRR for other benign lesions (12.0% vs. 19.4%; aRR, 0.67; 95% CI, 0.54-0.82) and negative (85.8% vs 77.3%; aRR, 1.06; 95% CI, 1.04-1.09) were statistically significant. All other colonoscopy findings did not differ significantly between the 2 age groups, including for advanced lesions (1.7% vs. 2.6%; aRR, 0.69; 95% CI, 0.39-1.22) and colorectal cancer (0.3% vs. 0.5%; aRR, 0.55; 95% CI, 0.19-1.57). In addition, there were no significant differences between age groups for all lesion types among women. Other than for other benign lesions and negative, there were no significant differences in the types of lesions among men. Conclusion: The current study findings extend the observation of similar screening colonoscopy detection rates for advanced lesions and colorectal cancer in those aged 40 to 49 years vs 50 to 59 years and support the suggestion that there is likely no need to reduce advanced lesions and colorectal cancer detection rate benchmarks because of the infusion of younger patients into the screening pool. The similar rates of advanced lesions and colorectal cancer detection between age groups also provide support for lowering the start of screening initiation to age 40 years. Keywords: Colorectal cancer; Screening Colonoscopy; advanced lesions Citation Format: Xiangyuan Qi, Xiaomei Wu, Bo Zhu. Screening colonoscopy yields among adults aged 40 to 49 years after new screening guidelines abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 5108.