Utility of methylated DNA markers for the diagnosis of malignant biliary strictures

Background and Aims: Early identification of malignant biliary strictures (MBS) is challenging, with up to 20% classified as indeterminants after preliminary testing and tissue sampling with endoscopic retrograde cholangiopancreatography (ERCP). We aimed to evaluate the use of methylated DNA markers (MDM) from biliary brushings to enhance MBS detection in a prospective cohort. Methods: Candidate MDMs were evaluated for their utility in MBS diagnosis through a series of discovery and validation phases. DNA was extracted from biliary brushing samples, quantified, bisulfite-converted, and then subjected to methylation-specific Droplet Digital Polymerase Chain Reaction (ddPCR). Patients were considered to have no malignancy if the sampling was negative and there was no evidence of malignancy after 1 year or definitive negative surgical histopathology. Results: Fourteen candidate MDMs were evaluated in the discovery phase, with top-performing and new markers evaluated in the technical validation phase. The top four MDMs were TWIST1, HOXA1, VSTM2B, and CLEC11A, which individually achieved AUC values of 0.82, 0.81, 0.83, and 0.78, respectively, with sensitivities of 59.4%, 53.1%, 62.5%, and 50.0%, respectively, at high specificities for malignancy of 95.2-95.3% for the final biologic validation phase. When combined as a panel, the AUC was 0.86, achieving 73.4% sensitivity and 92.9% specificity, which outperformed cytology and fluorescent in situ hybridization (FISH). Conclusions: The selected methylated DNA markers demonstrated improved performance characteristics for the detection of MBS compared to cytology and FISH. Therefore, MDMs should be considered viable candidates for inclusion in diagnostic testing algorithms.