ESTRO 2025 - Abstract Book

S1824

Clinical – Upper GI

ESTRO 2025

Opfermann KJ, et al. Adjuvant radiotherapy and lymph node status for pancreatic cancer: results of a study from the Surveillance, Epidemiology, and End Results (SEER) Registry Data. Am J Clin Oncol. 2014 Apr;37(2):112-6. Fietkau, R. et al. Randomized phase III trial of induction chemotherapy followed by chemoradiotherapy or chemotherapy alone for nonresectable locally advanced pancreatic cancer: first results of the CONKO-007 trial [abstract]. J. Clin. Oncol. 40 (Suppl. 16), 4008 (2022).

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Mini-Oral Dosimetric effects of respiratory and anatomical changes in the European PROTECT trial: Proton vs photon therapy in locally advanced esophageal cancer Sarah Eckholdt Jensen 1 , Hanna Rahbek Mortensen 1,2 , Ane Appelt 3 , Camilla Skinnerup Byskov 4 , Gilles Defraene 5 , Mai Lykkegaard Ehmsen 1 , Karin Haustermans 5,6 , Maria Fuglsang Jensen 1 , Ditte Sloth Møller 4,2 , Marianne Nordsmark 4 , Pieter Populaire 5,6 , Rune Slot Thing 7 , Lone Hoffmann 4,2 1 Danish Centre for Particle Therapy, Aarhus University Hospital, Aarhus, Denmark. 2 Department of Clinical Medicine, Faculty of Health Sciences, Aarhus University, Aarhus, Denmark. 3 Leeds Institute of Medical Research, University of Leeds, Leeds, United Kingdom. 4 Department of Oncology, Aarhus University Hospital, Aarhus, Denmark. 5 Department of Oncology – Laboratory of Experimental Radiotherapy, KU Leuven – University of Leuven, Leuven, Belgium. 6 Department of Radiation Oncology, University Hospitals Leuven, Leuven, Belgium. 7 Department of Oncology, Vejle Hospital, University Hospital of Southern Denmark, Vejle, Denmark Purpose/Objective: The European phase III PROTECT trial a,b randomizes patients with locally advanced esophageal cancer between proton (PT) or photon (XT) radiotherapy before surgery. This study evaluated the robustness toward setup and range uncertainties, and respiration on planning CT (pCT) and weekly control CTs (cCTs) for target coverage for the initial 20 patients enrolled at a single study site. Furthermore, the accumulated target dose coverage based on daily cone-beam CT (CBCT) imaging was examined. Material/Methods: Patients were randomized to receive PT (n=11) or XT (n=9). PT involved 2-3 posterior beams, while XT utilized 5-8 IMRT beams. Treatment plans delivered uniform target dose distribution of 50.4Gy (RBE) in 28 fractions. The clinical target volume accounting for respiratory motion (iCTV) should receive >95% of 50.4Gy (RBE) (V95% iCTV >99% for nominal plans). Treatment plans should be robust toward setup (5mm), range (3.5%, only PT), and respiration (V95% iCTV >96%) evaluated in 14 (PT) and six (XT) scenarios. The pCT treatment plan was recalculated on weekly cCT scans to evaluate target coverage; in case of dosimetric deviations, patients underwent adaptive re-planning (rCT). The robustness of treatment plans on the cCTs was also examined (PT: 2mm/3.5%, XT: 2mm). Daily CBCT enabled evaluation of daily delivered dose using synthetic CT models (RaySearch Laboratories) for PT and calibrated CBCT electron density curves (MIM Software) for XT. The calculated daily dose distributions were accumulated onto the pCT.