S780
Clinical - Lung
ESTRO 2026
5 Department of Medical Oncology, Koc University Faculty of Medicine, Istanbul, Turkey. 6 Department of Pulmonary Medicine, 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 Purpose/Objective: To evaluate the safety and failure patterns of adjuvant thoracic radiotherapy (RT) in patients with locoregionally advanced non–small cell lung cancer (NSCLC) who underwent induction chemoimmunotherapy and surgery, as determined by a multidisciplinary tumor board (MTB). Material/Methods: This retrospective study included 22 patients treated between 2020 and 2025 who received induction chemoimmunotherapy, oncological surgery, and adjuvant thoracic RT. Adjuvant RT was recommended for those with cN2 disease at diagnosis, positive surgical margin, PL3 or combinations of them per MTB guidance. All patients underwent four-dimensional CT simulation. Target volumes were defined on the average respiratory phase to account for full tumor motion, and RT was delivered using a simultaneous- integrated boost with intensity-modulated RT. Lung dose was calculated on the expiratory phase (V50) and the esophageal doses based on an integrated volume encompassing full respiratory motion. The primary endpoint was local control (LC); secondary endpoints included regional recurrence (RR), distant metastasis (DM), overall survival (OS), progression-free survival (PFS), and treatment-related toxicities. Results: The median age was 63 years (range, 42–84), and median PD-L1 expression was 40%. Adenocarcinoma accounted for 68% of cases, and squamous cell carcinoma for 32%. According to the 9th TNM edition, 64% of patients had IIIA, 23% IIIB, and 13% IVA disease. The most common induction chemoimmunotherapy regimen was carboplatin plus paclitaxel (71%), with nivolumab (38%). Chemotherapy and immunotherapy were delivered for a median of 4 (range: 3– 6) cycles. Following induction, 41% achieved a complete pathological response. All patients had cN2 disease at diagnosis and 9% exhibited PL3. The median prescribed RT dose was 59.4 Gy (range, 50–63 Gy) in 27 (range, 15-30) fractions. Maintenance immunotherapy was given to 91% of patients (median 13 cycles; range: 4–37). At a median follow-up of 68
months (range: 20–142), no local recurrence occured. One- and two-year RR rates were 0% and 5%, while DM rates were 9% and 18%. OS at 1, 2, and 5 years was 100%, 100%, and 91%, and PFS rates were 100%, 91%, and 81%, respectively. Grade 1-2, and 3 esophagitis occurred in 45% and 5%, respectively, with no grade 4-5 toxicities. Radiation-induced pneumonitis occurred in 1 patient (5%), and immunotherapy- related pneumonitis in 2 (9%). Conclusion: Adjuvant thoracic RT following induction chemoimmunotherapy and surgery demonstrated excellent LC and survival with minimal toxicity in locoregionally advanced NSCLC. This multimodality approach appears safe and may confer additional benefit in carefully selected high-risk patients. Keywords: lung cancer, immunotherapy, adjuvant radiotherapy Chest wall adverse events following stereotactic body radiotherapy in peripheral lung tumors: incidence and dosimetric factors Alexandra Giraldo-Marín 1 , Blanca Peregrín-Pastor 1 , Enar Recalde-Vizcay 1 , Noelia Peñacoba-Benjumea 1 , Alejandro Seoane-Ramallo 2 , Savannah Pié-Padró 2 , Mónica Ramos-Albiac 1 , Xavier Maldonado-Pijoan 1 , Abraham André Geng-Cahuayme 1 1 Radiation Oncology, Vall d'Hebron University Hospital, Barcelona, Spain. 2 Medical Physics, Vall d'Hebron University Hospital, Barcelona, Spain Purpose/Objective: To evaluate incidence and clinical characteristics of chest wall adverse events (CWAE) after thoracic SBRT, and analyse potential clinical and dose-volume risk factors associated with their development. Material/Methods: Retrospective single-center study was conducted from August 1, 2019, to December 31, 2024 including patients with peripheral lung lesions (primary tumors and metastases) treated with 4-5 fraction SBRT. All lesions were in contact or adjacent to chest wall (CW) or ribs. CWAE was graded according to CTCAE v5.0. Type II reirradiations were accepted1. CW and rib were contoured following guideline recommendations2,3.A case-control analysis was performed to assess differences in the development of CWAE. Univariable- analysis was performed using Fisher’s exact test (reporting OR and 95% CI) and Mann–Whitney U test for categorical and continuous variables, respectively. Correlations between dosimetric parameters and toxicity duration or onset were explored using Spearman’s ρ . Results: Digital Poster 2042
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