S831
Clinical - Lung
ESTRO 2026
Digital Poster 4092 Cardiac dose and survival outcomes following SBRT for primary and metastatic lung tumors: a substructure-based analysis Goda Kalinauskaite 1,2 , Samuel Füchtbauer 1 , Kerstin Rubarth 1,3 , Thao Nguyen 1,3 , Larisa Silvana Kilian 1 , Felix Mehrhof 1 , Daniel Zips 1 , Carolin Senger 1 1 Department of Radiation Oncology, Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and HumboldtUniversität zu Berlin, Berlin, Germany. 2 Berlin Institute of Health, Charité – Universitätsmedizin Berlin, Berlin, Germany. 3 Institut of Biometry and Clinical Epidemiology, Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and HumboldtUniversität zu Berlin, Berlin, Germany Purpose/Objective: This study investigates the association between radiation dose to the heart base and other cardiac substructures and overall survival (OS) following stereotactic body radiotherapy (SBRT) for central and ultracentral lung tumors. Material/Methods: A retrospective analysis was performed on patients treated within the SBRT registry (2011–2023). Autosegmentation was used to contour the whole heart and cardiac substructures, while the heart base, overlapping the ascending aorta and including coronary origins and the sinoatrial node, was manually contoured (1). Mean (Dmean) and near-maximum doses (D0.03, highest dose to 0.03 cc) were converted to equivalent 2 Gy fractions (EQD ₂ , α / β = 3 Gy). Optimal dose cut-points were defined to stratify patients into high- and low-dose groups. Cox regression models, adjusted for age, sex, tumor type, and volume, assessed the association between cardiac dose and OS. Results: Among 82 treated patients, 66 were evaluable for dosimetry of cardiac structures and survival analysis. Median age was 67 years; 68% were male. Most lesions were metastases (62.5%) and evenly split between central (54.5%) and ultracentral (45.5%) locations. Higher EQD ₂ Dmean to the left atrium (HR 2.89, p = 0.04) and superior vena cava (HR 2.56, p = 0.03), and higher D0.03 to the superior vena cava (HR 3.12, p = 0.004) and right ventricle (HR 2.23, p = 0.04) were independently associated with worse OS (Figure 1). A higher mean dose to the heart base showed a strong trend toward reduced survival (HR 3.70, p = 0.05).
day 43 (median; range 29-64). In the total cohort (n=110), agreement between predicted and measured volumes resulted in R ² 0.62 and PCC 0.79 (Figure 1A).In the subgroup enriched for tumour shrinkage (n=46 patients with tumour shrinkage between CBCT-1 and CBCT-2) agreement between predicted and measured volumes improved substantially with R ² 0.85, and PCC 0.92. (Figure 1B).Figure 2 displays model prediction in 2 individual patients, one with tumour growth during early RT and therefore excluded from the subgroup analysis, and a second with regression identified on all early CBCTs.
Conclusion: This study highlights the value of appropriate patient selection when validating models in clinical radiotherapy. Underlying assumptions of the model should be considered prior to applying it to all patients and pre-selecting suitable patients is a key step in implementing models safely into clinical practice. References: [1] Barrett S., Z.M.U., Enderling H., Marignol L., Predicting Individual Tumour Response Dynamics in Locally Advanced Non-Small Cell Lung Cancer Radiation Therapy; a Mathematical Modelling Study. IJROB 2024[2] Barrett S., et al., Predicting tumour volume reduction in non-small cell lung cancer: Independent validation of a single parameter PSI model. R&O, 2025 S1443-S1445[3] Sunassee, E.D., et al., Proliferation saturation index in an adaptive Bayesian approach to predict patient-specific radiotherapy responses. IIJROB, 2019[4] Prokopiou, S., et al., A proliferation saturation index to predict radiation response and personalize radiotherapy fractionation. Radiation Oncology, 2015. 10: p. 159. Keywords: Patient selection, predictive model
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