S936
Clinical - Mixed sites & palliation
ESTRO 2026
previously irradiated brain metastases. Material/Methods:
than in lung cancer. In crude analyses, performance status and extracranial disease showed strong associations with deviation directionality: compared with KPS 90–100, KPS 70–80 had lower odds of severe deviation (OR 0.28, 95% CI 0.12–0.67; p=0.004), and KPS ≤ 60 showed an even lower risk (OR 0.13, 95% CI 0.05–0.34; p<0.001). Likewise, presence of extracranial disease was associated with lower odds of severe deviation than absence (OR 0.24, 95% CI 0.13–0.46; p<0.001), suggesting that the GPA tends to underestimate survival in clinically favorable patients (good KPS, no extracranial burden). These patterns were consistent with the direction observed when adjusting for histology (breast vs lung) and GPA index. Conclusion: In WBRT-treated patients with brain metastases from lung and breast cancers, the predictive accuracy of the GPA varies by histology and prognostic score level: breast cancer and higher GPA are linked to increased probability of major deviation. Worse KPS and extracranial disease further contribute to inaccuracy, reinforcing the need for histology-aware, clinically calibrated GPA refinements in contemporary practice. References: Sperduto PW, et al. Summary report on the graded prognostic assessment: an accurate and facile diagnosis-specific tool to estimate survival for patients with brain metastases. J Clin Oncol. 2012;30(4):419- 425. doi:10.1200/JCO.2011.38.0527Sperduto PW, et al. Beyond an Updated Graded Prognostic Assessment (Breast-GPA): A Prognostic Index and Trends in Treatment and Survival in Breast Cancer Brain Metastases from 1985 to Today. Int J Radiat Oncol Biol Phys. 2020;107(2):334-343. Keywords: GPA, Breast cancer, Lung cancer, WBRT Repeat stereotactic radiosurgery for locally recurrent brain metastases: outcomes and dosimetric predictors of radionecrosis Ceren Atahan 1 , Evrim Tezcanli 1 , Gamze Ugurluer 1 , Alptekin Arifoglu 2 , Zeynep Ozen 2 , Banu Atalar 1 , Enis Ozyar 1 , Meric Sengoz 1 , Ufuk Abacioglu 1 1 Radiation Oncology, Acibadem University, Istanbul, Turkey. 2 Radiation Oncology, Acibadem Altunizade Hospital, Istanbul, Turkey Purpose/Objective: Local recurrence after stereotactic radiosurgery (SRS1) for brain metastases presents a therapeutic challenge, and optimal re-irradiation parameters remain unclear. This study evaluated local control (LC) and predictors of radiation necrosis (RN) after re-SRS (SRS2) in Digital Poster 5135
From January 2015 to March 2025, 40 patients with 59 recurrent brain metastases treated with SRS2 to the same lesion were retrospectively analyzed. Patients previously treated with whole-brain radiotherapy were excluded. Follow-up MRI scans were analyzed for local failure and radiographic RN according to RANO criteria. Kaplan–Meier method for LC and RN-free survival; Cox regression analysis for predictors and ROC curve analysis for cutoff values were performed using SPSS v27. Results: Median follow-up was 11 months (2–83). Median interval between SRS1 and SRS2 was 11 months (3– 43); median SRS2 prescription dose was 24 Gy (14–35) in median of 3 fractions (1–5) and median GTV diameter at SRS2 was 2.1 cm (0.3–7.6). One-year LC was 57.5% and one-year RN rate was 20%. Most RN events (90%) occurred within first year.ROC curve analysis defined optimal cutoff values for doses predictive of RN. SRS2 EQD ₂ (10) threshold of 33.6 Gy separated higher- and lower-risk groups, with one- year RN-free survival of 63.8% for > 33.6 Gy and 91.3% for ≤ 33.6 Gy (p = 0.007; AUC = 0.780, 95%CI 0.625– 0.934). For total EQD ₂ (10) (SRS1 + SRS2), threshold was 75 Gy, yielding RN-free survival of 63.2% vs 91.4% (p = 0.006; AUC = 0.764, 95%CI 0.610–0.918). One-year RN- free survival was 65.8% for SRS2 BED ₃ > 83.7 Gy vs 90.9% for ≤ 83.7 Gy (p = 0.013; AUC = 0.785, 95%CI 0.700–0.870) and 65.2% vs 91.0% for total BED ₃ > 177 Gy vs ≤ 177 Gy (p = 0.013; AUC = 0.774, 95%CI 0.690– 0.860). Across all comparisons, higher BED and EQD ₂ significantly increased RN risk without significantly improving LC.Factors including sex, age, histology, lesion location, re-irradiated metastases number, prior surgery, GTV/PTV diameters/volumes at SRS1–SRS2, conformity/heterogeneity/gradient indices, brain V5– V25 values, concurrent/adjuvant systemic therapy, and whether SRS2 was delivered in single/multiple fractions were not associated with LC or RN (p > 0.05). Conclusion: In this study with a limited number of patients, maintaining SRS2 prescription doses below defined threshold values appears to reduce the risk of RN without significantly compromising LC. Optimal dose schemes that balance efficacy and safety for re- irradiation should be validated in prospective studies. Keywords: reirradiation, radionecrosis, brain metastasis
Digital Poster 5149 Partially ablative body radiotherapy (PABR) for
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