ESTRO 2025 - Abstract Book

S1327

Clinical - Lung

ESTRO 2025

Material/Methods: Real-world data of 224 patients from two German tertiary cancer centres were retrospectively analysed. 73 patients completed CRT-IO with sequential durvalumab (85%, 62 patients) or concurrent and sequential nivolumab (15%, 11 patients) and 151 patients were treated with CRT alone. First site of failure and the time to first failure was compared between the CRT-IO and the CRT alone subgroup Results: All 224 patients were treated between 2012-2022 with thoracic irradiation to a total dose of at least 60 Gy (range: 60-66 Gy conventionally fractionated), all patients received two cycles of concurrent platinum-based chemotherapy, 81 (36%) patients received prior induction chemotherapy and 4 (2%) induction chemo-immunotherapy. Median follow-up for the entire cohort was 43.4 (range: 3.4-126.1) months, median overall survival (OS) was 52.2 (95%CI: 39.7-64.7) months (CRT-IO: not reached; CRT alone: 40.1, p<0.001). The median progression-free survival (PFS) was 11.0 (95% CI: 8.0-14.0) months in the entire cohort and 23.7 months (95%CI: 4.2-43.2) in the CRT-IO vs. 9.3 months (95%CI: 7.2-11.4) in the CRT alone cohort (p<0.001). At the end of follow-up 52.1% (38 patients) in the CRT-IO cohort were alive or dead without progression vs 39.1% (59 patients) in the CRT cohort. Multifocal progression (MFP) was diagnosed as first failure in 23.3 % of CRT-IO patients an 43.7 % of CRT patients (p=0.015). In the CRT-IO cohort 9.6 % of patients presented with isolated brain metastasis first (BM) vs 2.6 % in the CRT cohort (p=0.028). 6.8% vs. 6.0% and 8.2% vs. 8.6% of patients had isolated extracranial distant metastasis (ecDM) and loco-regional progression (LRP) first in the CRT-IO vs. CRT cohort, respectively. Median time to MFP, BM, ecDM and LRP in the CRT-IO vs. CRT cohort was 7.9 months, 11.0 months, 6.5 months and 6.6 months vs. 6.6 months, 5.1 months, 6.0 months and 17.9 months, respectively (p=0.437, 0.407, 0.752 and 0.315). Conclusion: We found significantly differing patterns of failure in Patients treated with CRT-IO vs. CRT alone for stage III NSCLC. CRT-IO patients presented significantly less frequent with MFP and more often with isolated BM as first failure. Again CRT-IO demonstrated vastly improved OS and PFS in this real-world cohort Proffered Paper Radiotherapy dose to non-emphysematous lung outperforms whole lung volume in predicting survival in non-small cell lung cancer patients Azadeh Abravan 1,2 , Fatemah-Alzahraa Gomaa 3 , Tereza Ruzickova 3 , Corinne Faivre-Finn 1,2 , Ahmed Salem 4,1 1 Division of cancer sciences, The University of Manchester, Manchester, United Kingdom. 2 Radiotherapy related research, The Christie NHS FT, Manchester, United Kingdom. 3 School of Medical Sciences, The University of Manchester, Manchester, United Kingdom. 4 Faculty of Medicine, Hashemite University, Zarqa, Jordan Purpose/Objective: The extent of lung emphysema, quantified on computed tomography (CT) using Hounsfield Unit (HU) thresholds, could serve as a valuable image-based biomarker in radiotherapy. Non-emphysematous lung regions may be more susceptible to radiotherapy-induced damage, potentially contributing to treatment-related morbidity and mortality. We investigated the association between radiotherapy dose to the whole lung and non-emphysematous lung regions and overall survival (OS) in patients with non-small cell lung cancer (NSCLC). Material/Methods: Data from 1,302 stage I-III NSCLC patients treated with curative-intent radiotherapy between 2016 and 2022 at a single institution were retrospectively analyzed. Non-emphysematous lung regions were defined as regions with HU > -950 on planning CT scans. To evaluate the association between clinical and dosimetric variables and Keywords: patterns of failure, NSCLC, chemoirradiation, 1630