B-382 Accurate and Early Detection of Colorectal Cancer Using a Multilocus DNA Methylation Markers-based Testing in Peripheral Blood Mononuclear Cells

Abstract

Abstract Background An effective blood-based method for the diagnosis of colorectal cancer (CRC) has not yet been developed. Molecular alterations of immune cells occur early in tumorigenesis, providing the theoretical underpinning for early cancer diagnosis. Therefore, we aimed to develop an effective multi-molecular simultaneous detection method based on peripheral blood mononuclear cells (PBMCs) to improve the diagnosis of early-stage CRC. Methods Candidate DNA methylation markers were first identified from PBMCs using the Infinium MethylationEPIC array in the discovery phase (Shandong cohort I, n = 100) and further validated via pyrosequencing and targeted bisulfite sequencing in validation phase (Shandong cohort II, n = 202). Then, a single-tube multiplex methylation-specific quantitative PCR assay (multi-msqPCR) for simultaneous detection of five markers was established in a pilot study. After that, a CRC prediction model (CPM) based on DNA methylation and multi-msqPCR method was construct and its diagnostic performance were evaluated using the area under the receiver operating characteristic curve (AUROC) in our multicenter cohort (n = 595). Results Five discriminative DNA methylation markers identified by Illumina 850K microarray were successfully validated to diagnose early-stage CRC. Multi-msqPCR showed a better discriminative performance and 10-time lower detection limit than single-molecule detection in early-stage CRC. The cross-validated AUROC for CPM for early-stage CRC was 0.91 (sensitivity = 81.18%; specificity = 89.39%), significantly higher than CEA (AUROC = 0.62). CPM assay also yielded a high degree of discrimination for advanced adenoma (AA) cases (AUROC = 0.85; sensitivity = 63.04%; specificity = 89.39%). Besides, detecting CPM in multiple cancer types implied a CRC-specific diagnostic value. Our follow-up data also demonstrated that CPM could detect early-stage CRC up to 2 years before current traditional diagnostic methods. Conclusions CPM, in combination with epigenetic biomarkers and the multi-msqPCR method, was promising, cost-effective, and easily implementable for routine clinical diagnosis of early-stage CRC.