ESTRO 2025 - Abstract Book

S1353

Clinical - Lung

ESTRO 2025

Purpose/Objective: Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) represent a front-line therapeutic regimen for patients with EGFR-mutated stage IV non-small cell lung cancer (NSCLC) [1] . Our study aimed to provide the first comparative assessment of the value of third-generation EGFR-TKIs and thoracic radiotherapy (TRT) with TKI alone. Material/Methods: We retrospectively collected patients with EGFR-mutated (exon 19 deletions or exon 21 mutations) stage IV NSCLC who were initiated on front-line therapy with third-generation EGFR-TKIs from 2018 to 2023. Patients were divided into TKI-alone and TKI+TRT groups according to whether or not TRT was added. A 1:1 propensity score matching (PSM) was implemented to decrease possible bias, and overall survival (OS), progression-free survival (PFS), and treatment-associated adverse events were assessed. Results: For all patients, the median follow-up was 28.0 months (range 14.7–59.4 months). After PSM, each group consisted of 63 patients. Compared with the PSM-matched TKI-alone group, the TKI+TRT group presented significantly better PFS (25.3 vs. 21.4 months, hazard ratio [HR] = 0.55, P = 0.0085) and OS (45.5 vs. 35.1 months, HR = 0.49, P = 0.03). In patients with exon 19 deletions, adding TRT resulted in better PFS than only TKI alone (31.5 vs. 23.3 months). In patients with exon 21 mutations, the median PFS was 25.3 and 17.0 months in the TKI+TRT and TKI-alone groups, respectively. Only 4.3% of patients in the TKI+TRT group developed grade ≥3 pneumonitis. Conclusion: Incorporating TRT resulted in a significant prognostic benefit in front-line third-generation EGFR TKIs, with acceptable side effects. Keywords: NSCLC, thoracic radiotherapy, EGFR mutation. References: 1.Ettinger DS, Wood DE, Aisner DL, Akerley W, Bauman JR, Bharat A, et al. NCCN guidelines insights: non-small cell lung cancer. version 2.2021. J Natl Compr Canc Netw. 2021;19(3):254-66. Poster Discussion Impact of Prescribing to the PTV on GTV Dose Heterogeneity in lung SBRT: Insight from EORTC Studies. Volha Hertsyk 1 , Nicolaus Andratschke 2 , Enrico Clementel 1 , Coreen Corning 1 , Corinne Faivre-Finn 3 , Catherine Fortpied 1 , Matthias Guckenberger 4 , Sarah M Kelly 1,5,6 , Ursula Nestle 7 , Cecile Le Pechoux 8 , Daniel Portik 1,9 , Ajra Secerov-Ermenc 10 , Luiza Souza 1 , Nick Reynaert 11 1 Headquarters, European Organization for Research and Treatment of Cancer (EORTC), Brussels, Belgium. 2 Department of Radiation Oncology, University Hospital Zürich, Zürich, Switzerland. 3 Department of Radiotherapy Related Research, The Christie NHS Foundation Trust & University of Manchester, Manchester, United Kingdom. 4 Department of Radiation Oncology, University Hospital Zürich, Zürich, Switzerland. 5 Quality and Excellence in Radiotherapy and Imaging for Children and Adolescents with Cancer across Europe in Clinical Trials (QUARTET), European Society for Paediatric Oncology (SIOP Europe), Brussels, Belgium. 6 Faculty of Medicine and Health Sciences, University of Ghent, Ghent, Belgium. 7 Department of Radiation Oncology, Kliniken Maria Hilf, Moenchengladbach, Germany. 8 Department of Radiation Oncology, Gustave Roussy, Paris-Saclay University, Villejuif, France. 9 Department of Radiation Oncology (Maastro), GROW Research Institute for Oncology and Reproduction, Maastricht University Medical Centre+, Maastricht, Netherlands. 10 Division of Radiotherapy, Institute of Oncology Ljubljana, Ljubljana, Slovenia. 11 Medical Physics Department, Institut Jules Bordet, Hôpital Universitaire de Bruxelles, Brussels, Belgium 2425

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