ESTRO 2025 - Abstract Book

S754

Clinical - CNS

ESTRO 2025

Conclusion: SRT is an effective treatment for VS, achieving high local tumor control rates across all Koos grades with manageable acute and long-term toxicities. Female gender is a key predictor for radiation-induced facial spasms, emphasizing the need for targeted patient counseling. These findings provide critical insights for tailoring treatment plans and improving long-term quality of life in VS patients.

Keywords: retrospective, vestibular schwannoma, stereotactic

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Poster Discussion A dose-response meta-analysis for myelopathy in re-irradiation of non-spinal cord tumors Ahmed Salem 1,2 , Shatha Althyabat 3 , Naila Ararawi 3 , Louai Alsaloumi 4 , Sara Alawadat 3 , Sadeel Alsawalqah 3 , Batool Alsari 3 , Fanar Al-Samarat 3 1 Department of Anatomy, Physiology and Biochemistry, The Hashemite University, Zarqa, Jordan. 2 Division of Cancer Sciences, University of Manchester, Manchester, United Kingdom. 3 Faculty of medicine, The Hashemite University, Zarqa, Jordan. 4 Department of Applied Pharmaceutical Sciences and Clinical Pharmacy, Isra University,, Amman, Jordan Purpose/Objective: Re-irradiation is increasingly used worldwide. Spinal cord myelopathy is a grave complication of re-irradiation due to increasing the cumulative dose delivered to the spinal cord. This dose-response meta-analysis aimed to evaluate the effect of cumulative biological effective dose (BED) on the incidence of spinal cord myelopathy and compare proton vs photon re-irradiation of non-spinal cord tumors. Material/Methods: We conducted a comprehensive literature review using the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. We screened 11,972 studies available for review up to May 2024. Included studies reported toxicity following photon or proton re-irradiation in any tumor site where the spinal cord was within the designated radiation field. To ensure lack of bias, we excluded all studies on the re-irradiation of spinal cord tumors. Studies on brachytherapy re-irradiation were also excluded. Only English-published literature was included. A dose-response meta-analysis was conducted to evaluate the relationship between the cumulative re irradiation dose to the spinal cord (cumulative BED in Gy, using α/β ratio=2) and the incidence of myelopathy. Results: A total of 47 studies (2,611 patients) were eligible for data extraction. Only three papers (83 patients) reporting on proton re-irradiation were included, representing only 3.2% of the overall study population. No cases of myelopathy were reported in this patient subset. Due to the small number of patients, studies on proton re-irradiation were omitted from the analysis preventing us from comparing the incidence of spinal cord myelopathy in proton vs photon re-irradiation. There were 30 cases (1.2%) of myelopathy in the 44 studies (2,528 patients) of photon re irradiation which were included in the meta-analysis. The mean cumulative BED in myelopathy cases was 153.1 Gy (range, 100-222.2 Gy. The mean time interval between radiotherapy course 1 and 2 for myelopathy cases was 1.4 months (range, 0.75-6 months). Meta-regression revealed a statistically significant positive association between cumulative BED and the incidence of myelopathy (QM (1) =4.28, p=0.0385). Specifically, for each 1 Gy increase in the cumulative BED, the logit-transformed incidence of myelopathy increased by 0.0093 (95% CI: 0.0005-0.0181)