Circulating tumor DNA in biliary tract cancers: challenges, opportunities, and clinical readiness.

Biliary tract cancers have a poor prognosis, with tumor location and desmoplasia often restricting tissue acquisition for molecular profiling. Circulating tumor DNA is a minimally invasive alternative with expanding clinical utility, although technical and standardization challenges limit its routine adoption. We review evidence, limitations, and strategies supporting large-scale validation for real-time monitoring and personalized treatment.