ESTRO 2025 - Abstract Book

S1294

Clinical - Lung

ESTRO 2025

We screened 571 records to include nine RCTs (mostly at low risk of bias) with 712 participants (338 males), using radiotherapy as radical local therapy. Add-on radical radiotherapy improved OS by 40% [Hazard ratio: 0.60, 95% CI 0.48-0.75; high certainty of evidence]. Between-trial heterogeneity does not affect the results, only leading to a 4% difference [MHR 1.04]. Add-on radical radiotherapy leads to longer OS by 0.33 months (0.12-0.54), 1.97 months (0.26-3.68), 3.95 months (1.19-6.71), and 7.24 months (3.81-10.67) over one, two, three, and four years. Radical radiotherapy was well tolerated with no major safety concerns. Conclusion: Add-on radical radiotherapy – chiefly stereotactic radiotherapy – is beneficial in oligometastatic NSCLC. Future studies may address the role of additional PD-L1 expression and the related immunotherapy in this group of patients. References: 1. Peng P et al. EGFR-TKIs plus stereotactic body radiation therapy (SBRT) for stage IV Non-small cell lung cancer (NSCLC). Radiother Oncol. Jul 2023;184:109681. doi:10.1016/j.radonc.2023.109681 2. Tsai CJ et al. Standard-of-care systemic therapy with or without stereotactic body radiotherapy in patients with oligoprogressive breast cancer or non-small-cell lung cancer: an open-label, randomised, controlled, phase 2 study. Lancet. Jan 13 2024;403(10422):171-182. doi:10.1016/S0140-6736(23)01857-3 3. Gomez DR, Tang C, Zhang J, et al. Local Consolidative Therapy Vs. Maintenance Therapy or Observation for Patients With Oligometastatic Non-Small-Cell Lung Cancer. J Clin Oncol. Jun 20 2019;37(18):1558-1565. doi:10.1200/JCO.19.00201 Digital Poster Predicted Outcome Benefits of Static and Dynamic Proton Arc Therapy Compared to Intensity-Modulated Proton Therapy for Non-Small Cell Lung Cancer Arno C. Hessels, Robin Wijsman, Bas A. de Jong, Erik W. Korevaar, Anneke Maring, Chimène I. Werkman, Stefan Both, Johannes A. Langendijk Radiation Oncology, 1University Medical Center Groningen, Groningen, Netherlands Purpose/Objective: Proton arc therapy (PAT) uses multiple gantry angles, potentially reducing the dose to organs at risk (OAR) compared to intensity-modulated proton therapy (IMPT). While static PAT (sPAT) is delivered with static gantry angles, dynamic PAT (dPAT) involves gantry rotation during dose delivery. Tumour movement and tumour tissue-air interfaces in thoracic cancers like non-small cell lung cancer (NSCLC) complicate proton treatment planning due to density uncertainties, which may degrade tumour coverage. This study evaluates the potential impact of PAT on treatment outcomes and robust target coverage for NSCLC patients. Material/Methods: Twenty NSCLC patients qualified for IMPT based on predicted reduction in normal tissue complication probability (ΔNTCP) compared to photon radiotherapy. sPAT plans were created using 120 energy layers and 15 gantry angles with an energy layer filtering (ELF) algorithm. dPAT plans used a 1-degree gantry angle spacing and an early energy layer selection and spot assignment (ELSA) algorithm with a maximum of 360 energy layers (330 used on average). All treatment plans were robustly optimized in RayStation (2023B) with 6-mm setup/ 3% density uncertainty. Similar optimization objectives were used for target and OARs. Inter-fraction robustness was evaluated per fraction and cumulatively over weekly CTs using a voxel-wise-minimum distribution based on 28 scenarios with 2-mm setup / 3% density uncertainty. NTCP for esophagitis, pneumonitis, and 2-year mortality, as well as average and cumulative Keywords: oligometastases, radical radiotherapy, lung cancer 216