ESTRO 2025 - Abstract Book

S1759

Clinical – Upper GI

ESTRO 2025

804

Digital Poster Ultra- and Moderately Hypofractionated Radiotherapy for Inoperable Cholangiocarcinoma: A single institution retrospective analysis Saheli Saha 1 , Cameron Lee 2 , Michael Yan 1 , Ali Hosni Abdalaty 1 , Jelena Lukovic 1 , Rebecca Wong 1 , Aisling Barry 1 , John Kim 1 , James Brierley 1 , Bernard Cummings 1 , Jennifer Knox 3 , Chaya Shwaartz 4 , Laura A Dawson 1 , Aruz Mesci 1 1 Department of Radiation Oncology, Princess Margaret Cancer Centre, Toronto, Canada. 2 Department of Radiation Oncology, University of Toronto, Toronto, Canada. 3 Medical Oncology, Princess Margaret Cancer Centre, Toronto, Canada. 4 Department of Surgery, University of Toronto, Toronto, Canada Purpose/Objective: The objectives of the study were to assess overall survival (OS),progression-free survival (PFS), post-treatment hospitalization, and patterns of recurrence following radiotherapy (RT) for patients with inoperable localized cholangiocarcinoma (CCA). Material/Methods: Retrospective data of patients with a diagnosis of primary, non-metastatic intrahepatic cholangiocarcinoma (iCCA), periportal cholangiocarcinoma (hCCA), or extrahepatic cholangiocarcinoma (dCCA) who underwent curative-intent RT (at least BED 10 of 32.5 Gy) between 01/Jan/2004 to 1/Jun/2022 were collected. OS and PFS were calculated from the first date of RT. The Kaplan-Meier method was used for survival analysis. Univariable analysis for age, type of CCA, baseline and post-RT CA 19-9, pre-radiation biliary obstruction, prior chemotherapy, PTV volume, BED, and overall treatment time (OTT) was performed using the Cox proportional hazard model. Results: In total, 56 patients with a median age of 67.5 years (range 38-90) met the inclusion criteria. Of those, 44 (78.6%) had iCCA, 8 (14.3%) had dCCA, and 4 (7.1%) had hCCA. Chemotherapy was administered in 23 (41.1%). Forty-three patients (76.8%) received SBRT; the remainder received moderately hypofractionated RT (mHFX). Concurrent chemotherapy was not administered. The median RT dose was 36Gy (25-58.05) in 6 (5-20) fractions, BED 10 of 55Gy (37.5-102.6). Four (7.1%) patients did not complete the full RT course. The median follow-up was 11.4 months. Median OS and PFS were 13.5 months (95% CI 14,22) and 4.3 months (95% CI 6,14), respectively. Pre-radiation biliary obstruction was associated with worse OS (p=0.01). Elevated baseline CA 19-9 level (p= 0.04) and larger lesion size (mm) (p <0.005) were associated with worse PFS; decreased OS and PFS were noted with increased age (p=0.03). Local control, regional control, and extrahepatic metastasis-free survival were 64.6%,69.5%, and 72.2%, respectively, at 1 year. The predominant recurrence pattern post-RT was the appearance of out-of-field new liver lesions (n=24, 64.9%). Conclusion: This study shows the potential role of radiotherapy in local control. However, it also highlights the high propensity of intrahepatic disease progression and underscores the need for better case selection and judicious decisions on the role of RT in inoperable CCA.

Keywords: cholangiocarcinoma, inoperable, hypofractionatedRT