S783
Clinical - Lung
ESTRO 2026
Oncology, Koc University Faculty of Medicine, Istanbul, Turkey. 3 Department of Medical Oncology, Koc University Faculty of Medicine, Istanbul, Turkey. 4 Department of Medical Oncology, American Hospital, Istanbul, Turkey. 5 Department of Pulmonary Medicine, American Hospital, Istanbul, Turkey. 6 Department of Thoracic Surgery, American Hospital, Istanbul, Turkey. 7 Department of Thoracic Surgery, Koc University Faculty of Medicine, Istanbul, Turkey. 8 Department of Radiology, American Hospital, Istanbul, Turkey. 9 Department of Radiology, Koc University Faculty of Medicine, Istanbul, Turkey. 10 Department of Nuclear Medicine, American Hospital, Istanbul, Turkey. 11 Department of Nuclear Medicine, Koc University Faculty of Medicine, Istanbul, Turkey. 12 Department of Pathology, Koc University Faculty of Medicine, Istanbul, Turkey
incidence of symptomatic brain metastases between the groups.
Purpose/Objective: To assess the safety and failure patterns of
consolidative thoracic hypofractionated radiotherapy (RT) following induction chemoimmunotherapy and evaluation for surgical candidacy in patients with locally advanced, inoperable non-small cell lung cancer (NSCLC). Material/Methods: This retrospective study included 34 patients with unresectable locally advanced NSCLC treated between 2019–2025. All received induction chemoimmunotherapy followed by consolidative hypofractionated thoracic RT based on multidisciplinary tumor board recommendation. Four- dimensional CT simulation was performed, and target volumes were delineated on the average respiratory phase to account for tumor motion. RT planning included a simultaneous-integrated boost using intensity-modulated techniques. Lung dose was evaluated on the expiratory phase (V50), and esophageal constraints were based on a composite motion-inclusive volume. The primary endpoint was local control (LC); secondary endpoints were regional recurrence (RR), distant metastasis (DM), overall survival (OS), progression-free survival (PFS), and treatment-related toxicity. Results: Median age was 64 years (range: 33–78) and median PD-L1 expression 20% (range: 0–95%). Histology included squamous cell carcinoma (56%) and adenocarcinoma (38%). According to 9th TNM edition was IIB in 12%, IIIA in 27%, IIIB in 38%, and IIIC in 23%. The most common systemic regimen was carboplatin plus paclitaxel (74%) with nivolumab (59%). Median induction cycle numbers were four for both chemotherapy (range: 2–6) and immunotherapy (range: 2–9). Post-induction response included complete in 21%, partial in 62%, stable in 12%, and progressive in 6%. Median RT dose was 52.5 Gy (range:
Keywords: PCI, LD-SCLC, SCLC
Digital Poster 2119 Failure Patterns After Induction Chemoimmunotherapy and Definitive Hypofractionated Thoracic Radiotherapy in Inoperable Locally Advanced NSCLC Caglayan Selenge Beduk Esen 1 , Sukran Senyurek 2 , Duygu Sezen 2 , Fatih Selcukbiricik 3 , Kerim Kaban 4 , Metin Kanitez 4 , Perran Fulden Yumuk 4 , Nil Molinas Mandel 4 , Levent Tabak 5 , Ezgi Cesur 6 , Suat Erus 7 , Serhan Tanju 7 , Sukru Dilege 6,7 , Terman Gumus 8 , Cetin Atasoy 9 , Cengiz Demirkurek 10 , Okan Falay 11 , Mehmet Onur Demirkol 10,11 , Pinar Bulutay 12 , Pinar Firat 12 , Merve Duman 2 , Saliha Ezgi Oymak 1 , Nulifer Kilic Durankus 2 , Yasemin Atagun 1,2 , Ugur Selek 1,2 1 Department of Radiation Oncology, American Hospital, Istanbul, Turkey. 2 Department of Radiation
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