Integration of circulating tumor DNA in biliary tract cancer: the emerging landscape.

Precision medicine has emerged as a cornerstone in cancer treatment revolutionizing our approach across malignancies. Molecular profiling of biliary tract cancers (BTCs) has changed the treatment landscape positively by prolonging survival in an aggressively fatal malignancy in its advanced stages. The acquisition of tissue tumor DNA for genomic analysis in BTC is often anatomically challenging, limited by quantity and quality. In response, ctDNA has emerged as a noninvasive means of molecular profiling. The utility of both plasma and bile ctDNA has been explored in several studies demonstrating the high mutation detection rates and the ability to isolate targetable mutations when present. In addition, the concordance between plasma and tissue DNA provides validity in utilizing ctDNA results to infer treatment decisions. Analysis of ctDNA in BTC has also provided prognostic information and facilitated evaluation of clonal evolution with ease of serial measurements. Insight into novel mechanisms of resistance to targeted therapies are being uncovered in ctDNA. As research endeavors continue to deepen our understanding in the field particularly in the space of ctDNA surveillance after curative intent, the tremendous progress made so far has enabled integration of ctDNA into the clinical practice of BTCs.