Immunotherapy in Advanced Biliary Tract Cancers

SIMPLE SUMMARY: A new era has emerged in oncology in the last ten years with the development of immune therapies. However, single-agent immune therapy such as immune checkpoint inhibitors seems to have a limited clinical activity in biliary tract cancers and are still largely investigational, except for the few patients with microsatellite-instable tumors. Here, we review: (i) the molecular and immune landscape of biliary tract cancers, (ii) the existing results of immune therapies in biliary tract cancers, and (iii) the future of immune therapies in biliary tract cancers, with the identification of predictive biomarkers for response to these therapies, and the ongoing therapeutic trials. ABSTRACT: Biliary tract cancers are rare tumors with a poor prognosis. Two-thirds of these primary liver malignancies are diagnosed at advanced stages where therapeutic options are limited. Whereas several molecular targeted therapies emerge in biliary tract cancers, immunotherapy is still investigational, the only approved immunotherapy to date being the immune checkpoint inhibitor pembrolizumab for the small fraction of patients with microsatellite-instable tumors. In microsatellite-stable, pre-treated biliary tract cancers, single-agent immune checkpoint blockade has a limited albeit often long-lasting clinical activity in a still ill-defined subgroup of patients. The identification of predictive biomarkers will allow a better selection of patients that may benefit from immunotherapy. Combinations of immunotherapies with each other, with chemotherapy or targeted molecular therapies are being investigated in early lines of therapy, including first-line.