Role of ctDNA in Genetic Profiling & Outcomes for Advanced BTC

Biliary tract cancer (BTC) is a rare and heterogeneous disease with high incidence and mortality in Korea. Molecular profiling has enabled the identification of actionable alterations such as Isocitrate Dehydrogenase 1 (IDH1) mutations, FGFR2 fusions, ERBB2 amplifications, and dMMR/MSI-H status. However, the utility of tumor tissue-based next-generation sequencing (NGS) is often limited by difficulties in obtaining adequate tissue samples and the lack of in-house sequencing capacity across many hospitals. Circulating tumor DNA (ctDNA) analysis offers a minimally invasive alternative that can provide rapid and reliable genomic profiling. In a previous study, ctDNA testing showed high concordance with tissue-based genomic profiling for clinically significant alterations, particularly IDH1 mutations, and identified additional mutations not detected in tumor tissue. These findings suggest that ctDNA may expand access to targeted therapies such as ivosidenib . This multicenter, prospective, observational epidemiology study, organized by the Korean Cancer Study Group (KCSG) Biliary Tract Cancer Subcommittee, will evaluate the clinical utility of ctDNA-based genomic profiling in patients with advanced BTC. The study will assess concordance between ctDNA and tumor tissue sequencing, describe the prevalence of actionable alterations, and explore the impact of ctDNA testing on treatment decisions and clinical outcomes. By leveraging a nationwide network of BTC specialists, this study seeks to validate ctDNA as a feasible and scalable tool for precision oncology, supporting timely and personalized therapy for patients with BTC.