Biliary tract cancers: advances in diagnostic and management.

Biliary tract cancers (BTCs) are aggressive malignancies associated with poor prognosis and limited treatment options. Advances in precision oncology, notably the identification of recurrent molecular alterations such as fibroblast growth factor receptor 2 (FGFR2) fusions, isocitrate dehydrogenase 1 (IDH1) mutations, ERBB2 amplifications, and v-Raf murine sarcoma viral oncogene homolog B (BRAF) V600E mutations, have introduced new therapeutic avenues and modest survival benefits for patients with advanced disease. However, the practical implementation of targeted therapies remains hampered by challenges in tumor tissue acquisition and molecular testing, highlighting the need for alternative genomic profiling strategies. This comprehensive review examines the role of liquid biopsy as a non-invasive strategy for molecular profiling in BTCs, with a focus on the clinical applications of plasma and bile-derived circulating tumor DNA (ctDNA). We synthesized findings from recent clinical studies evaluating mutation detection rates, concordance between liquid biopsy and tissue-based assays, and the comparative performance of plasma versus bile ctDNA. Liquid biopsy demonstrates high rates of mutation detection and good concordance with tissue analyses. Bile-derived ctDNA, owing to its proximity to the tumor, consistently shows higher sensitivity and mutant allele frequencies (MAFs) than plasma ctDNA. Nevertheless, challenges remain, including lower sensitivity for detecting structural alterations (e.g., gene fusions), variability in ctDNA yield depending on disease status, and a lack of assay standardization across platforms. Liquid biopsy, particularly through bile ctDNA analysis, emerges as a promising adjunct to tissue biopsy for molecular profiling in BTCs. It offers opportunities for earlier, less invasive, and more personalized treatment decisions. Future directions should aim at developing tumor-informed liquid biopsy strategies that increase precision, reduce costs, and ultimately improve patient outcomes. Prospective studies are needed to confirm its clinical utility and survival impact.