Abstract 3656: Target enrichment of methylated circulating tumor DNA for colorectal cancer detection

Abstract Aberrant DNA methylation changes are one of the earliest signatures of cancer development. Methylation profiling of circulating tumor DNA (ctDNA) from plasma has emerged as a promising approach for early cancer detection (ECD). However, the set of methylation targets that can successfully distinguish cancer through liquid biopsy will vary depending on cancer type and subtype. Here, we explored a methylation target enrichment workflow and developed a methylation-based classification model to distinguish between patients with colorectal cancer (CRC) and healthy individuals. First, CRC-specific CpG targets were identified by comparing the methylation landscape of CRC and normal samples (tissue and blood) available in The Cancer Genome Atlas (TCGA) database and Gene Expression Omnibus (GEO) datasets. This analysis resulted in 800 CRC-specific CpG targets for initial evaluation. To develop and test the classification model, CRC patients and healthy individuals with plasma samples were included. A machine learning model was used to evaluate the highest performing CpG targets that effectively discriminated between CRC patients with detected ctDNA (“CRC ctDNA-positive”) and healthy individuals. Correlation between methylation levels of the high performing CpG targets and the variant allele frequency (VAF) among CRC ctDNA-positive patients was calculated. In total, 86 patients were included in this proof of concept study (mean age, 62 ±12 years; male, 55%). 50 CRC ctDNA-positive patients (24% stage I, 40% stage II, 24% stage III, and 12% stage IV) and 36 healthy normals were included in the analysis. We investigated this cohort to identify the highest performing CpG targets among the 800 potential CpG targets that provided effective discrimination between CRC patients and healthy individuals. Using the highest performing CpG targets, observed methylation level was correlated with VAF of single nucleotide variants detected by ctDNA testing (R2: 0. 8). In summary, we developed a cost-effective methylation target enrichment workflow and utilized machine-learning algorithms to demonstrate the potential use of ctDNA methylation markers in early detection. Additional studies are needed to confirm that these and other markers can accurately distinguish between patients with CRC and healthy individuals. Citation Format: Hsiao-Yun Huang, Ravi Vijaya Satya, Wen-Ching Chan, Esha Atolia, Joshua Babiarz, Bernhard Zimmermann, Trupti Kawli. Target enrichment of methylated circulating tumor DNA for colorectal cancer detection abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 3656.