S769
Clinical - Lung
ESTRO 2026
2 Heidelberg Ion Beam Therapy Center (HIT), Heidelberg University Hospital, Heidelberg, Germany. 3 Department of Thoracic Surgery, Thoraxklinik at Heidelberg University Hospital, Heidelberg, Germany Purpose/Objective: Primary tracheal tumors are rare, accounting for 0.03% of all cancers with an incidence of 0.14 per 100,000 [1]. Adenoid-cystic carcinoma (ACC) is the second most common subtype after squamous cell carcinoma, typically diagnosed late due to indolent growth and nonspecific symptoms [2, 3]. Submucosal and perineural spread often prevents complete resection, and late recurrences are common [2]. Treatment typically involves surgery with postoperative radiotherapy (RT). Evidence remains limited and largely based on photon RT, whereas carbon-ion and combined-modality RT have shown benefit in head and neck ACC, but data for tracheobronchial ACC (TACC) are scarce [3, 4].We report preliminary outcomes from one of the largest TACC cohorts treated with photon, carbon-ion (C12), or combined RT in postoperative and definitive settings, providing a benchmark for future particle-therapy approaches. Material/Methods: After ethics approval (S-421-2015), patients with histologically confirmed TACC treated at the Heidelberg University Hospital, Department of Radiation Oncology (2005–2024) were included. Clinical data were retrieved from records, and acute toxicity graded per CTCAE v5.0. Follow-up was calculated by the reverse Kaplan–Meier method. Survival was analyzed using Kaplan–Meier and log- rank tests, and cumulative incidence functions with competing risks assessed local, regional, and distant progression. Recurrence was defined by consensus imaging review or biopsy confirmation. Results: Seventy-one patients met inclusion criteria; 41 received definitive and 30 postoperative RT. Treatment comprised IMRT + carbon-ion (C12) boost in 45, IMRT alone in 16, and C12-only RT in 10 patients. Median follow-up was 44.5 months. Overall, 12 deaths and 31 progressions occurred, predominantly distant failures. Five- and ten-year overall survival were 91% and 65%, progression-free survival 36% and 13%, and distant metastasis-free survival 50% and 27%, respectively. The five- and ten-year cumulative incidence of local recurrence was 22% and 39%, and of distant metastasis 40% and 44%. Overall survival did not differ between bronchial vs. tracheal ACC or between definitive vs. postoperative RT. Grade ≥ 3 acute toxicity occurred in 9%, most commonly stridor. Conclusion: In this cohort of patients with tracheobronchial ACC, carbon-ion RT achieved overall survival outcomes that
toxicities included tachyarrhythmia and congestive heart failure, followed by pericarditis and ischemic events. In multivariable analysis, prior stroke (OR 4.17; 95% CI, 1.09-15.98; p = 0.04) and primary lung tumor (OR 4.03; 95% CI, 1.12-14.42; p = 0.03) independently increased cardiotoxicity risk. At 24 months, freedom from local failure was 78.3%, while cumulative incidences of local and distant recurrence were 15.5% and 30.4%, respectively. Eighteen deaths occurred (16.6%); 2-year OS was 83.4% (95% CI, 73.8-89.7). In the Cox model, pacemaker implantation markedly increased mortality risk (HR 6.78; 95% CI, 1.54-29.80; p = 0.01), whereas each additional +10 Gy EQD ₂ was associated with improved OS (HR 0.73; 95% CI, 0.53- 0.99; p = 0.04). Conclusion: Cardiac toxicity following SBRT for central and ultracentral lung tumors occurred in approximately 8% of patients, typically emerging one year after treatment. Prior cerebrovascular disease and pulmonary primaries identified patients at particularly elevated risk, and pacemaker implantation was associated with poorer survival. These findings underscore the importance of systematic cardio- oncology follow-up and dose-aware treatment planning, particularly in anatomically constrained settings. References: -Timmerman R. Stereotactic Body Radiation Therapy for Inoperable Early Stage Lung Cancer. JAMA. 2010;303:1070. -Bezjak A, Paulus R, Gaspar LE, et al. Safety and Efficacy of a Five-Fraction Stereotactic Body Radiotherapy Schedule for Centrally Located Non– Small-Cell Lung Cancer: NRG Oncology/RTOG 0813 Trial. J Clin Oncol. 2019;37:1316–1325. -Walls GM, Bergom C, Mitchell JD, et al. Cardiotoxicity following thoracic radiotherapy for lung cancer. Br J Cancer. 2025;132:311–325. -El-Rayes M, Nardi Agmon I, Yu C, et al. Lung Cancer and Cardiovascular Disease: Common Pathophysiology and Treatment-Emergent Toxicity. JACC CardioOncol. 2025;7(4):325–344. Keywords: Cardiac toxicity, SBRT, Ultracentral lung tumors Digital Poster Highlight 1223 Survival outcomes after carbon-ion–based radiotherapy for tracheobronchial adenoid cystic carcinoma Stella Winter 1 , Philipp Schröter 1 , Katharina Kozyra 1,2 , Hin Lau 1 , Katharina Dvornikovich 1 , Florian Stritzke 1 , Nils Netzer 1 , Lukas Bauer 1 , Fabian Weykamp 1 , Klaus Herfarth 1,2 , Semi B Harrabi 1,2 , Andrea Mairani 1,2 , Hauke Winter 3 , Jürgen Debus 1,2 , Thomas Held 1,2 1 Heidelberg Institute of Radiation Oncology (HIRO), Heidelberg University Hospital, Heidelberg, Germany.
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