Role of Radiation Therapy for Biliary Tract Cancers.

Biliary tract cancers include cholangiocarcinoma, gallbladder cancer, and ampullary cancer. Although overall rare, the incidence is increasing globally, particularly the subset of intrahepatic cholangiocarcinoma. Surgery is currently considered to be the only curative treatment approach; however, survival outcomes after surgery remain poor. Moreover, many patients already have advanced-stage, unresectable disease at the time of diagnosis. Herein, we will review the role of adjuvant radiotherapy to improve local control after surgery, the role of neoadjuvant radiotherapy to increase the proportion of patients able to undergo surgery, and the use of definitive/palliative radiotherapy to provide local control/symptom relief for patients who have inoperable disease. Most studies observed a survival benefit associated with radiotherapy, with the strongest evidence for those with high-risk disease features (e.g., positive surgical margins, lymph node involvement). However, due to the low incidence of biliary tract cancers, most existing studies are retrospective; there is very limited randomized data and prospective studies tend to have small sample sizes, underscoring the need for more high-quality research on radiotherapy for biliary tract cancers. As some studies show evidence of a dose-dependent response, further investigation into the delivery of dose-escalated radiotherapy with modern techniques such as proton therapy is warranted.