Blood Circulating Tumor DNA‐based Genomic Profiling and Serial Analysis in Patients With Advanced Biliary Tract Cancer

Background/Aim: This study aimed to identify mutation profile similarities between tissue and circulating tumor DNA (ctDNA) and to explore driver mutations as potential prognostic or predictive biomarkers or druggable targets in patients with advanced biliary tract cancer (BTC). Patients and Methods: We prospectively enrolled 18 patients with advanced BTC and analyzed next‑generation sequencing data from 60 ctDNA samples using AlphaLiquid^® 100. This assay screens up to 118 genes for single‑ nucleotide variants (SNVs) and insertion or deletions (INDELs), 27 genes for copy number alterations (CNAs), and 10 genes for fusions. We examined the intra‑patient tissue‑ctDNA concordance and studied the association between ctDNA variant allele frequency (VAF) and survival. Results: A total of seven gallbladder cancer cases, six intrahepatic cholangiocarcinoma cases, and five extrahepatic cholangiocarcinoma cases were observed. Among these cases, tumor tissues were available for 16 patients. Genetic alterations were detected in 88% (14/16) of tissue DNA samples and 89% (16/18) of samples with ctDNA at baseline. The most common genes altered in ctDNA were TP53 (n=11), ERBB3 (n=3), and KRAS (n=3). There was a 29% overlap in somatic SNVs/INDELs and a 60% overlap in CNAs between tissue DNA and ctDNA, while no fusion variant was detected. The sensitivity and positive predictive value of ctDNA for all types of somatic mutations were 47% and 43%, respectively. Among the 14 patients whose serial ctDNA was analyzed, 10 showed changes in ctDNA. A high pre‑treatment VAF (>4.0%) was associated with poor overall survival. Conclusion: ctDNA sequencing can successfully identify molecular genetic alterations in patients with advanced BTC, providing insights into potential biomarkers and therapeutic targets.