S777
Clinical - Lung
ESTRO 2026
where feasible, with MDT approval for radiologically diagnosed lesions. SF SABR necessitated peripheral tumours with PTV not abutting critical structures, and minimal motion <1.5cm. Endpoints included OS, PFS, and acute and chronic toxicities graded as per CTCAE v5.0. Statistical analysis comprised Wilcoxon rank sum and Fisher exact tests, competing risk models for local recurrence, and 1:1 PSM adjusting for age, sex, smoking status, performance status, histology, T- stage, and follow-up duration. Results: The study included 71 patients with peripheral early- stage NSCLC, 38 receiving single-fraction (SF) SABR and 33 receiving multi-fraction (MF) SABR (Table 1). Median survival was not reached in the SF group and was 43.23 months in the MF group, with no significant difference in overall survival (P = 0.313) or local recurrence rates (P = 0.594). One SF patient and two MF patients experienced local recurrence, with no distant recurrences observed. Three-year survival was 68.4% versus 53.5%, and three-year local control exceeded 95% in both groups. Treatments were well tolerated with no grade 3–4 toxicities observed. After PSM, 30 patients remained per group, eliminating baseline differences in T-stage and involved lobe. Outcomes remained comparable, with three-year survival 69.4% versus 55.4% and local control 94.5% versus 95.4%. Conclusion: Our findings indicate that 34 Gy single-fraction SABR is a safe, effective, and efficient alternative to 54 Gy in three fractions for peripheral early-stage NSCLC, with comparable local control, survival, and toxicity. Broader adoption may be supported by ongoing real- world data collection and targeted clinician education. Keywords: Single fraction, SABR, SBRT, lung cancer, NSCLC Digital Poster 1886 Supporting Informed Decision-Making in Small Cell Lung Cancer: An Environmental Scan on Prophylactic Cranial Irradiation Information Provision Katie E Dixon 1 , Marianne Aznar 1 , Hilary L Bekker 2 , Corinne Faivre-Finn 1,3 1 Cancer Science, University of Manchester, Manchester, United Kingdom. 2 Leeds Institute of Health Sciences, University of Leeds, Leeds, United Kingdom. 3 Clinical Oncology, The Christie NHS Foundation Trust, Manchester, United Kingdom Purpose/Objective: Prophylactic cranial irradiation (PCI) for small cell lung cancer (SCLC) reduces the risk of brain metastases by approximately 50% and improves overall survival.
shows no cardiac adverse events within one year after dose-escalated SBRT. No cases of peri- or myocarditis occurred during follow-up, despite substantially exceeding the respective heart maximum dose constraints according to Timmerman et al. in eight patients. More liberate maximum dose constraints could be discussed for tumors abutting the heart. However, the observed increase in E/e' ratio alongside a “pseudonormal” E/A ratio suggests a decline in diastolic function, possibly indicating radiogenic myocardial fibrosis. Further research is necessary to refine dose constraints for cardiac substructures and preserve myocardial function. References: Timmerman R. A Story of Hypofractionation and the Table on the Wall. Int J Radiat Oncol Biol Phys. 2022 Jan 1;112(1):4-21. doi: 10.1016/j.ijrobp.2021.09.027. PMID: 34919882. Keywords: Dose escalation, MR-guided SBRT, ultracentral stereotactic radiotherapy for early-stage NSCLC: a two-centre experience and propensity matched analysis Sumeet Hindocha 1 , Kohgulakuhan Yogalingam 2 , Caroline Maguire 3 , Jim Daniel 2 , Robin Inkersole 2 , Clive Peedell 2 , Crispin Hiley 4 1 Medical Physics & Biomedical Engineering, University College London, London, United Kingdom. 2 Clinical Oncology, South Tees Hospital NHS Foundation Trust, Middlesbrough, United Kingdom. 3 Clinical Oncology, University College London Hospitals NHS Foundation Trust, London, United Kingdom. 4 Cancer Institute, University College London, London, United Kingdom Purpose/Objective: Stereotactic Ablative Body Radiotherapy (SABR) is a standard-of-care for medically inoperable patients with early-stage NSCLC, with high local control (LC) and low toxicity. Single fraction (SF) SABR offers comparable outcomes to multi-fraction (MF) regimens, yet despite its efficacy, cost-savings, and patient convenience, it remains under-utilised. We report outcomes following 34Gy SF for early-stage peripheral NSCLC across 2 UK cancer centres. Using propensity score matching (PSM), we evaluate difference in LC, overall survival (OS) and toxicity versus 54Gy/3 fractions. Material/Methods: Patients receiving 34 Gy SF SABR (2020–2024) at South Tees and UCLH were compared with a 54Gy/3- Digital Poster Highlight 1880 34Gy single fraction vs 54Gy in 3 fraction fractions cohort at UCLH. All underwent CT and FDG- PET staging; histological confirmation was obtained
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