<i>NR3C1</i> , <i>LAX1</i> , and <i>RCAN3</i> as Circulating Epigenetic Biomarkers for Prognosis and Chemotherapy Response Prediction in Metastatic Pancreatic Cancer

ABSTRACT Pancreatic cancer remains highly lethal, largely due to late diagnosis and limited efficacy of treatments. Improving first‐line treatment selection and patient monitoring requires novel, non‐invasive biomarkers beyond carbohydrate antigen 19‐9 (CA19‐9) and imaging. This study investigates epigenetic biomarkers from liquid biopsy with prognostic and predictive potential in metastatic pancreatic ductal adenocarcinoma (PDAC; mPDAC). Genome‐wide methylation profiling of cell‐free DNA (cfDNA) from healthy individuals and stage IV mPDAC patients identified 13 gene‐associated CpG sites with significantly altered methylation patterns. ddPCR validation confirmed consistent methylation differences in lymphocyte transmembrane adaptor 1 ( LAX1 ), nuclear receptor subfamily 3 group C member 1 ( NR3C1 ), and RCAN3 between healthy and patient groups. Elevated LAX1 and RCAN3 methylation and reduced NR3C1 methylation at diagnosis were associated with poor prognosis and correlated with high‐risk circulating biomarker profiles, including CA19‐9 levels, RAS MAF (mutant allele fraction), cfDNA concentration, and cfDNA fragmentation. Notably, baseline NR3C1 methylation levels predicted response to first‐line FOLFIRINOX‐based treatment with an acceptable 75% sensitivity and a high specificity of 92.86%. These findings highlight the clinical significance of cfDNA methylation as a minimally invasive biomarker source, emphasizing LAX1 , NR3C1 , and RCAN3 as prognostic biomarkers in mPDAC. Specifically, baseline NR3C1 methylation emerges as a promising predictor of treatment response, supporting personalized therapeutic strategies in mPDAC.