Colorectal cancer screening using a multi-locus blood-based assay targeting circulating tumor DNA methylation: a cross-sectional study in an average-risk population

Abstract Background Effective screening for colorectal cancer (CRC) enables earlier diagnosis and intervention to improve patient survival. Methods In this study, we prospectively conducted a blood-based CRC screening program for community residents in Hanjiang District, Yangzhou City, and evaluated the screening efficacy of a blood-based multi-locus DNA methylation assay (ColonAiQ). The ColonAiQ-positive rate and colonoscopy participation rate of the population, detection rate of intestinal lesions, and positive predictive value (PPV) of CRC and advanced adenoma (AA) were calculated, and the associated factors were explored. Results A total of 105,285 participants were enrolled from January 2021 to December 2022, all of whom completed the ColonAiQ assay, yielding a positive rate of 6.42% (6759/105,285). The colonoscopy compliance rate was 48.56% (3282/6759). Intestinal lesions were detected in 1773 individuals (54.02%), including 63 cases of CRCs (predominately early-stage), 1195 adenomas (441 cases of AAs), 327 polyps, and 188 other benign lesions. CRC patients exhibited higher ColonAiQ scores and more positive loci compared to healthy individuals. The PPVs were 1.92% for CRC and 13.44% for AA. Among participants, 66,121 (62.8%) completed questionnaires graded by the Asia–Pacific Colorectal Screening score, with 12,139 (18.36%) classified in the high-risk tier. High-risk participants had a higher ColonAiQ-positive rate (11.07%) and PPVs for CRC (3.46%) and AA (22.18%). Factors associated with increased detection rates for CRC and AA included male gender, older age, a history of alcohol consumption, and prior polyps. Conclusions Our study demonstrated that ColonAiQ assay effectively identifies high-risk population. These findings strongly suggest that the ColonAiQ assay represents a promising strategy for the early detection of CRC and AA in individuals at average risk. Trial registration Registered at ClinicalTrials.gov (NCT05336539).