Yield of Fecal Immunochemical Test Screening for Colorectal Cancer in Adults Aged 45–49 vs 50–54 Years

INTRODUCTION: The rising incidence of early-onset colorectal cancer (CRC) has prompted debate over lowering screening initiation age. However, real-world evidence on fecal immunochemical test (FIT)-based screening effectiveness in 45-49 years remains limited. The aim of our study was to evaluate screening yield of FIT-based CRC screening between 45-49 and 50-54 years. METHODS: Conducted within a provincial CRC screening program in China, this study used 2-sample FIT screening followed by colonoscopy for positive results. Screening outcomes, including FIT positivity, colonoscopy completion, positive predictive values (PPVs) and detection rates of adenoma and advanced colorectal neoplasia, were compared between participants aged 45-49 and 50-54 years. Robust Poisson regression was used to estimate adjusted risk ratios (aRRs), using 50-54-year-old age group as reference. RESULTS: Among 733,137 participants, 89,446 were aged 45-49 years and 643,691 aged 50-54 years. Participants aged 45-49 years had higher FIT positivity (10.61%) and colonoscopy completion (46.75%) than those aged 50-54 years. However, detection rates for advanced neoplasia (0.30% vs 0.39%; aRR, 0.78; 95% confidence interval [CI], 0.68-0.88) and any adenoma (0.78% vs 0.95%; aRR, 0.83; 95% CI, 0.77-0.90) were significantly lower in the younger group, with similar results observed for PPVs. Within the 45-49-year-old age group, comparable detection rates to 50-54-year-old age group were observed among individuals with established risk factors, most notably among smokers (RR, 1.50; 95% CI, 1.22-1.84), frequent alcohol drinkers (RR, 1.33; 95% CI, 1.01-1.75), and men (RR, 1.20; 95% CI, 1.03-1.40). DISCUSSION: Overall, adults aged 45-49 years showed higher screening participation but lower screening yield than those aged 50-54 years. These findings highlight the importance of prioritizing individuals with elevated risk profiles for CRC screening in younger populations.