ESTRO 2025 - Abstract Book

S1835

Clinical – Upper GI

ESTRO 2025

The 6-month actuarial overall survival were 75%, 58%, and 21% for M0-cRT, M0-pRT, and M1-pRT, respectively. M1 patients treated with pRT had a significantly worse OS (2.8 months) compared to M0 patients (9.8 months, p=0.037). 26 palliative treated patients (72%) had a clinical benefit. Palliative treated patients who showed a clinical benefit had a median OS of 9.6 months, compared to 2.9 months for those with no benefit. Toxicity was acceptable, with 12 patients (29%) requiring a nasogastric tube during or after treatment, and 1 patient developing acute grade 3 skin toxicity. No grade ≥ 4 toxicities were reported. Conclusion: A clinical benefit after palliative reirradiation was found in 72% of the patients. Palliative patients who had a clinical benefit from the treatment had an median OS of 9.6 months compared to 2.9 months in patients who had no benefit. Non-metastatic patients treated with curative radiotherapy had a significant better OS compared to non metastatic patients treated with palliative radiotherapy.

Keywords: Reirradiation, palliation

3545

Digital Poster Unexpected large variations in target and OAR delineations in SBRT for perihilar cholangiocarcinoma - QA of a prospective multicentre trial Suus Y. van Loosbroek 1 , Maaike T.W. Milder 1 , François Willemssen 2 , Wilhelm den Toom 1 , Martijn Intven 3 , Gert J. Meijer 3 , Christelle Bouchart 4 , Akos Gulyban 5 , Eva Versteijne 6 , Anna M. Bruynzeel 6 , Miguel A. Palacios 6 , Ines Joye 7,8 , Matthias Hermans 7 , Jeroen Buijsen 9 , Richard Canters 9 , Pètra M. Braam 10 , Ruud G.H. van Leeuwen 10 , Margriet Dieters 11 , Fred J.F. Ubbels 11 , Vincent C. Hamming 11 , Ben Heijmen 1 , Alejandra Méndez Romero 1 1 Department of Radiotherapy, Erasmus MC Cancer Institute, University Medical Center Rotterdam, Rotterdam, Netherlands. 2 Department of Radiology and Nuclear Medicine, Erasmus MC University Medical Center Rotterdam, Rotterdam, Netherlands. 3 Department of Radiation Oncology, University Medical Center Utrecht, Utrecht University, Utrecht, Netherlands. 4 Department of Radiation Oncology, Hôpital Universitaire de Bruxelles (H.U.B.) - Institut Jules Bordet, Université Libre de Bruxelles (ULB), Brussels, Belgium. 5 Department of Medical Physics, Hôpital Universitaire de Bruxelles (H.U.B.) - Institut Jules Bordet, Université Libre de Bruxelles (ULB), Brussels, Belgium. 6 Department of Radiation Oncology, Amsterdam UMC Location VUmc, Amsterdam, Netherlands. 7 Department of Radiation Oncology, Iridium Netwerk, Wilrijk – Antwerp, Belgium. 8 Centre for Oncological Research (CORE)-IPPON, University of Antwerp, Faculty of Medicine and Health Sciences, Wilrijk – Antwerp, Belgium. 9 Department of Radiation Oncology (Maastro), GROW Research Institute for Oncology and Reproduction, Maastricht University Medical Centre+, Maastricht, Netherlands. 10 Department of Radiation Oncology, Radboud University Medical Center, Nijmegen, Netherlands. 11 Department of Radiation Oncology, University Medical Centre Groningen, Groningen, Netherlands Purpose/Objective: Quality assurance (QA) has enhanced treatment efficacy in prospective clinical radiotherapy trials (1). We developed a QA program to achieve consistent stereotactic body radiation therapy (SBRT) treatment for a rare tumour within a prospective multicentre trial. In this abstract, we focus on quantitative analyses of contouring on a benchmark case. Material/Methods: QA was conducted as part of the STRONG II trial (NCT06493734), which aims to investigate the efficacy of SBRT in patients with unresectable perihilar cholangiocarcinoma (2). Six participating centres, directly involved in patient treatment, took part in the trial QA prior to patient inclusion. The target (tumour and pathological lymph nodes) and the relevant organs at risk (OARs) were delineated on a contrast-enhanced planning CT. Diagnostic CT and MR imaging, endoscopic reports and medical references of the patient were provided to aid delineation. Submitted