EP13.05 STEREOTACTIC RADIOSURGERY FOR MENINGIOMA - SINGLE CENTRE EXPERIENCE ON SAFETY AND SEIZURE

Abstract BACKGROUND Stereotactic radiosurgery (SRS) is a treatment option for meningioma that are untreated or recurrent after surgery and fractionated radiotherapy. The local control rate after SRS is around around 95% at 5 years. The incidence of seizure after SRS is approximately 5-15%. The purpose of our study is to evaluate the risk of seizure after SRS at our centre. MATERIAL AND METHODS Patients treated within a 2-year period from March 2023 to March 2025 were analysed. SRS dose was 16Gy /1 fraction or 25Gy/5 daily fractions for larger meningiomas (e.g. >10cc) or in order to meet organ-at-risk dose constraints. MRI head with contrast is performed after 6 months to evaluate response. RESULTS 56 patients with 60 meningiomas were treated. The median follow-up duration was 242 days. The median volume of meningioma was 4.7cc (range 0.21-17.7cc). 50 meningiomas were treated with 16Gy/1 fraction (median volume 4.69cc) and 10 with 25Gy/5 fractions (median volume 12.7cc). 34 patients had no prior treatment for meningioma while 22 patients had recurrence after surgery including 7 who also had adjuvant fractionated radiotherapy. Following SRS four patients developed seizure. 2 patients had no prior treatment, 1 had prior surgery and 1 had prior surgery and adjuvant radiotherapy. The mean time to seizure was 141 days (range 89 - 189 days). MRI head at the time of seizure showed that 3 patients had increased perilesional oedema and meningioma changes consistent with radionecrosis while 1 patient had no apparent radiological change. Seizures were managed with anti-epileptic medication. Independent samples t-test showed no statistical difference in meningioma volume, prescribed dose or brain dose (V12Gy, D50%) between patients who developed seizures compared to those who did not. The analysis was limited by the small number of patients who developed seizure. CONCLUSION SRS for meningioma is safe and associated with a low seizure risk of 7% at our centre. Further work, with a larger sample size and longer follow up period is needed to determine the risk factors of seizures after SRS for meningioma.