# Role of Radiation Therapy for Biliary Tract Cancers

## TL;DR

This paper reviews how radiation therapy can help treat biliary tract cancers, especially when surgery isn't possible, and highlights the need for more research.

## Contribution

The paper systematically reviews the role of radiotherapy in biliary tract cancers and emphasizes the need for modern techniques and high-quality studies.

## Key findings

- Radiotherapy improves outcomes for biliary tract cancer patients, especially those with advanced-stage disease.
- Most studies show a survival benefit from radiotherapy, particularly in high-risk cases like positive surgical margins.
- Modern radiotherapy techniques like proton therapy may offer better results and require further investigation.

## Abstract

Biliary tract cancers include cholangiocarcinoma (cancer of the bile ducts), gallbladder cancer, and ampullary cancer (cancers occurring at confluence of the common bile duct and pancreatic duct). Survival outcomes for biliary tract cancers are poor despite surgical intervention, and many patients are unable to undergo surgery due to advanced disease at the time of cancer diagnosis. Thus, radiotherapy, either before surgery, after surgery, or in place of surgery with either curative or palliative treatment intent, may improve outcomes for patients with biliary tract cancers. Herein, we discuss the current literature investigating radiotherapy for biliary tract cancers. Most studies show a benefit to radiotherapy, with the strongest evidence for those with advanced-stage disease. Further study is needed, particularly prospective clinical trials and evaluation of contemporary radiotherapy techniques that may allow for dose escalation (e.g., proton therapy and stereotactic body radiotherapy).

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.