1159 - Fourteen-Year Single-Institution Experience Using MRI-Guided SBRT on an Orthotopic Liver Transplantation Protocol for Unresectable Cholangiocarcinoma
Presenter(s)
T. C. Wu, J. Goldman, P. T. Courtney, and A. Raldow; Department of Radiation Oncology, University of California, Los Angeles, Los Angeles, CA
Purpose/Objective(s):
To evaluate the efficacy of MRI-guided SBRT (MRgSBRT) as bridging radiation therapy in combination with chemo(immuno)therapy prior to orthotopic liver transplantation (OLT) for unresectable cholangiocarcinoma (CCA).
Materials/Methods:
This retrospective study reviewed patients with localized, unresectable CCA treated with MRgSBRT from 2012 to 2026 at a single high-volume transplant center. Patients received MRgSBRT to the primary lesion followed by consolidation chemo(immuno)therapy as a bridging strategy until OLT or disease progression. The cohort was stratified into two groups: those successfully bridged to OLT and those who did not reach transplant (dropout group). Primary endpoints included Overall Survival (OS) and Time to Progression (TTP). Continuous variables were compared using the Mann-Whitney U test, and survival outcomes were analyzed using the Kaplan-Meier method.
Results:
Over a 14-year period, 38 patients were identified (31 hilar, 7 intrahepatic); 25 (66%) were male with a median age of 58.0 years (IQR: 53.5–64.1). Median follow-up for the entire cohort was 24.8 months. The median PTV was 95.1 cc (IQR: 55.4–135.5 cc), with 50 Gy in 5 fractions being the most common prescription. Patients successfully bridged to OLT (n=11, 29%) demonstrated a significant survival advantage over those who dropped out (n=27), achieving a median OS of 59.9 months vs. 16.6 months ($p < 0.001$) and a 2-year survival rate of 90.0% vs. 20.8%, respectively. Among those transplanted, the pathologic complete response (pCR) rate was 36% (4/11). In the dropout cohort (median follow-up 15.4 months), 48.1% (n=13) developed locoregional progression with a median TTP of 10.6 months (IQR: 5.3–15.7 months); notably, no in-field local failures were observed. MRgSBRT was well-tolerated; 25% of patients experienced low-grade adverse events, with one Grade 4 duodenal ulcer reported.Conclusion:
MRgSBRT is a safe and effective bridging strategy for unresectable CCA, providing durable local control with no observed in-field failures. While locoregional progression remains the primary driver of transplant dropout—highlighting a need for more effective systemic therapies—successful bridging to OLT offers a profound survival advantage.