2947 - Clinical Outcomes and Risk Stratification in Unresectable Biliary Tract Cancers Undergoing Radiation Therapy

U. Amit Sr^1,2, S. Misra³, J. P. Plastaras¹, J. M. Metz¹, T. B. Karasic⁴, M. Lubas⁵, and E. Ben-Josef¹; ¹Department of Radiation Oncology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, ²Department of Radiation Oncology, Tel Aviv Medical Center, Tel Aviv, Israel, ³Department of Radiotherapy, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, India, ⁴Division of Hematology and Oncology, University of Pennsylvania, Philadelphia, PA, ⁵Fox Chase Cancer Center, Philadelphia, PA, United States

Purpose/Objective(s): Biliary tract cancers (BTC) are rare and aggressive malignancies originating from intrahepatic and extrahepatic bile ducts and the gallbladder. Surgery is the only curative option, but due to late-stage diagnosis, is frequently not feasible, leaving chemotherapy as the primary treatment. Radiotherapy (RT) can be an effective alternative for patients with unresectable, non-metastatic BTC despite the generally poor prognosis and significant variability. We aimed to identify prognostic markers that could aid in predicting overall survival (OS) and guide patient management. Materials/

Methods: A retrospective cohort study of 78 patients with unresectable BTC treated with definitive intent RT was conducted at a single institution. Comprehensive demographic, clinical, and treatment-related data were extracted from the electronic medical records. Univariate and multivariate Cox regressions were employed to identify OS predictors. A biomarker model was developed for refined survival prediction.
Results: The cohort primarily comprised patients with good performance status without significant hepatic dysfunction at presentation. The predominant treatment approach involved hypofractionated RT or concurrent fluorouracil-based chemoRT. Median OS was 12.3 months, and 20 patients (15.6%) experienced local progression with a median time of 30.1 months. Univariate and multivariate analyses identified CA19-9 (above median) and higher albumin-bilirubin (ALBI) grades at presentation as significant predictors of poor OS. Median OS was 24 months for patients with no risk factors and 6.3 months for those with both.
Conclusion: Our study demonstrates generally poor but significantly heterogeneous OS in patients with unresectable BTC treated with RT. We have developed a biomarker model based on CA19-9 and ALBI grade at presentation that can distinguish sub-populations with markedly diverse prognoses. This model can aid the clinical management of this challenging disease.