ESTRO 2025 - Abstract Book

S1291

Clinical - Lung

ESTRO 2025

Conclusion: Patients with LA-NSCLC who completed ≥ 20 cycles of consolidation durvalumab had significantly better survival rates than those who discontinued treatment. Durvalumab should be administered for more than 6 months to achieve the primary benefit of consolidation therapy after dCRT. Asian patients may have a different profile in terms of EGFR-mutant LA-NSCLC compared to Western patients.

Keywords: durvalumab, NSCLC, immunotherapy

References: 1. Doi H, et al. Optimal duration of consolidation durvalumab following chemoradiotherapy in stage III non-small cell lung cancer: a multi-institutional retrospective study. Target Oncol. 2024. [In press]. 2. Hellyer JA, et al. Role of Consolidation Durvalumab in Patients With EGFR- and HER2-Mutant Unresectable Stage III NSCLC. J Thorac Oncol. 2021;16:868-872.

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Digital Poster Is there a clinical consequence of CTV omission in SBRT of NSCLC? Philipp Reinhardt 1,2 , Ilya Kotov 3,1 , Daniel Schmidhalter 4 , Olgun Elicin 1 , Daniel Hendrik Schanne 1

1 Department of Radiation Oncology, Inselspital Bern, University Hospital and University of Bern, Bern, Switzerland. 2 Diagnostic, Interventional, and Pediatric Radiology, University Hospital and University of Bern, Bern, Switzerland. 3 Center for Proton Therapy, Paul Scherrer Institute, Villigen, Switzerland. 4 Division of Medical Radiation Physics and Department of Radiation Oncology, University Hospital, and University of Bern, Bern, Switzerland Purpose/Objective: The use of CTV margins in lung SBRT is not a standard practice, primarily due to historically high local control (LC) rates and potential concerns regarding increased toxicity. However, there is a lack of comprehensive data assessing the necessity of defining a CTV margin. In this study, we evaluated LC outcomes in patients treated with lung SBRT and examined the relationship between LC and dose coverage within a hypothetical CTV margin. Material/Methods: This retrospective study included 126 patients (median age: 72 years; range: 53–89) with 140 pulmonary lesions, comprising histopathologically confirmed (46%) or clinically diagnosed (54%) primary lung cancers. Patients with a BED below 100 Gy were excluded. Hypothetical CTVs (hCTV) were generated with a 6 mm margin for squamous cell carcinoma and an 8 mm margin for adenocarcinoma or clinically diagnosed lesions, and further expanded to hypothetical PTVs (hPTV). A ring structure (rCTV) was defined by subtracting the GTV from the hCTV. DVH parameters for original and hypothetical volumes, as well as the ring structure, were analyzed. Local failure was determined by pathology reports or multidisciplinary tumor board decisions based on imaging. Principal component analysis (PCA) was performed to address multicollinearity among DVH parameters, with the resulting components used as predictors in multivariable analysis to evaluate associations with local control. Results: SBRT was delivered with a median BED of 124 Gy (range: 100–151 Gy). The 3-year LC rates were 83.3%, 80.5%, 66.9%, and 71.0% for lesion diameters of ≤10 mm, 11–20 mm, 21–30 mm, and ≥31 mm, respectively. Univariate analysis showed that LC was significantly associated with the percentage of rCTV receiving a BED ≥100 Gy (rCTV_vol_BED100; HR 0.98; 95% CI: 0.96–1.00; p = 0.047). Additional significant correlations were found for the GTV receiving 90% (HR 0.98; 95% CI:0.96–1.00; p = 0.045) and 100% (HR 0.97; 95% CI: 0.96–0.99; p = 0.009) of the BED. After PCA reduced highly correlated parameters, a multivariable model identified a significant correlation between rCTV_vol_BED100 and LC rate (HR 0.98; 95% CI: 0.96–1.0; p = 0.042). No significant associations were found for FEV1 (HR 0.83; 95% CI: 0.43–1.60; p = 0.575) or GTV (HR 1.00; 95% CI: 0.98–1.00; p = 0.938).