ESTRO 2025 - Abstract Book

S106

Invited Speaker

ESTRO 2025

reviewed by an oncologist. Each centre performed both RIR and DIR for each case and transferred OARs and 3D dose distributions from previous CT-images to the current CT-images. All data were analysed centrally. Based on the study results, the trial recommends the use of DIR, except in cases with large anatomical changes. 2. Dose planning for reirradiation is complex. The current plan should account for the previous dose, and the cumulative equieffective dose (EQD2) must be evaluated. The RTQA group investigated whether the centres could comply with trial dose constraints. The study aimed at refining and evaluating the feasibility of the trial dose planning guidelines. Six cases were distributed to all centres, including physical 3D dose distributions of previous treatment rescaled to EQD2 (α/β=3, except spinal cord: α/β=2) and transferred to the current planning-CT, as well as targets and OARs delineated on current CT. The centres optimized plans using local treatment planning software. Dose distributions for current plan and EQD2 summed plans were analysed centrally. After four cases were completed, a workshop was conducted to discuss prioritisation between OAR constraints and target coverage. Consensus was reached to respect OAR constraints over target coverage, and the centres reoptimized plan four and completed cases five and six. 3. OARs must be delineated on CT image sets from three test-patients and approved by the QA group. The RTQA group will perform on-trial QA. Each centre must submit images, delineations and dose distributions for the first two patients treated for review by the RTQA group. Further continuous QA will be performed. Data on previous radiotherapy, systemic treatments, and surgery, including grade 3-4 thoracic toxicity, is collected at baseline. Clinical follow-up, including thoracic CT-imaging, is performed every three months until three years and bi-annually thereafter. Early and late radiotherapy-related toxicity is scored by CTCAE. The EORTC quality of life questionnaires C30 and LC13 are used to evaluate patient-reported outcomes. The EQ-5D-5L questionnaire is used to describe the health state. It will also be evaluated whether the patients experience decision regret regarding reirradiation.

[1] Andratschke2022

4821

Speaker Abstracts Evidence-based palliative radiotherapy in the IO era Yvette van der Linden Radiotherapy, LUMC, Leiden, Netherlands. Centre of Expertise in Palliative Care, LUMC, Leiden, Netherlands

Abstract:

The combination of palliative radiotherapy and immunotherapy (IO) has generated considerable interest as a potential strategy in cancer treatment. This talk will review the current evidence from scientific literature regarding the synergistic potential between these therapies, focusing on the biological rationale, such as the abscopal effect, where localized radiotherapy may induce systemic immune responses. While early studies suggest promising outcomes, concerns remain regarding the risks of increased toxicity, costs, and the complexity of combining treatments. The talk will cover existing guidelines, ongoing clinical trials, and relevant case reports, offering a balanced perspective on the effectiveness and safety of this combination in various cancer types. The session will also touch upon the challenges in optimizing these therapies and outline areas where future research may help clarify their potential role in cancer care.