# Defining the Role of Adjuvant Radiotherapy for Biliary Tract Cancers: A Site-Specific Propensity-Matched Analysis

## TL;DR

This study shows that adjuvant radiotherapy improves survival for some biliary tract cancers but not others, highlighting the need for personalized treatment strategies.

## Contribution

The study provides site-specific evidence on the effectiveness of adjuvant radiotherapy for different biliary tract cancer subtypes.

## Key findings

- Adjuvant radiotherapy significantly improves survival for gallbladder cancer, especially in node-positive or R1-resected patients.
- Radiotherapy benefits bile duct cancers compared to no treatment but offers limited advantages over chemotherapy alone.
- No survival benefit from radiotherapy was observed for intrahepatic cholangiocarcinoma.

## Abstract

Biliary tract cancers represent a group of rare malignancies with a generally poor prognosis, even after potentially curative surgery. Additional treatments such as chemotherapy and radiotherapy are often used to improve survival, but their effectiveness varies depending on the cancer type. In this study, we analyzed data to determine the impact of radiotherapy for different biliary cancer subtypes. We found that adjuvant radiotherapy significantly improves survival for gallbladder cancer, particularly in patients with lymph node involvement or incomplete tumor removal (R1). For bile duct cancers, radiotherapy is beneficial compared to no treatment but offers limited advantages over chemotherapy alone. For intrahepatic cholangiocarcinoma, no survival benefit was observed with radiotherapy. These findings emphasize the need for tailored treatment strategies based on the specific type of biliary tract cancer.

Background: Biliary tract cancers (BTCs) have distinct tumor biology but share a poor prognosis, with a 5-year-survival-rate of 5–19%. Surgical resection is the only potential cure, but recurrences are common. The role of adjuvant radiotherapy (XRT) remains unclear. Methods: Using the National Cancer Database (2006–2018), we analyzed resected non-metastatic BTCs. Patients who survived beyond 90 days post-surgery were included, while those with R2 resections or neoadjuvant therapy were excluded. Propensity matching was performed based on predictors of adjuvant radiation, age, and sex. Survival outcomes were compared between no adjuvant therapy, chemotherapy alone, and XRT ± chemotherapy. Results: Among 21,275 patients, including 5308 intrahepatic cholangiocarcinoma (IHC), 2689 perihilar cholangiocarcinoma (PHC), 3092 distal cholangiocarcinoma (DCC), and 10,186 gallbladder cancer (GBC) cases, adjuvant XRT did not improve survival for IHC. For PHC and DCC, XRT improved survival over no adjuvant therapy (PHC: 31.2 vs. 26.3 months, p = 0.004; DCC: 33.7 vs. 27.0 months, p = 0.015) but not over chemotherapy alone. For GBC, XRT significantly improved survival compared to both no adjuvant therapy and chemotherapy (30.2 vs. 26.6 and 24.6 months; p = 0.05 and p = 0.001). Conclusions: XRT provides a survival benefit for GBC, especially in node-positive and R1-resected patients. For PHC and DCC, XRT improves outcomes compared to no therapy, but its benefit over chemotherapy is uncertain. No benefit was observed for IHC.