Biliary tract cancers (BTCs) are frequently diagnosed in advanced stages and are highly lethal. Immunotherapy may play a role in the treatment of these patients. Promising results come from monotherapy or combination therapy studies in pretreated patients. In addition, several studies have demonstrated the safety and efficacy of immune checkpoint inhibitors (ICIs) in combination with chemotherapy in treatment-naive patients. Numerous biomarkers have been investigated to define their predictive role in response to ICIs. However, the full extent of the benefit of immunotherapies has not yet been fully established and, except for high microsatellite instability status, no other biomarkers were uniquely predictive of response to ICIs.
Keywords: PD-L1; biliary tract cancer; immune checkpoint inhibitors; microsatellite instability; predictive biomarkers; tumor microenvironment; tumor mutational burden.