P17.45.A SEIZURE MANAGEMENT IN PATIENTS WITH EPILEPSY FROM BRAIN METASTASES: THE EFFECTIVENESS OF LEVETIRACETAM VERSUS OTHER FIRST-LINE ANTISEIZURE MEDICATION MONOTHERAPIES

Abstract BACKGROUND Brain metastases (BMs) are the most common malignant brain tumors. Approximately 25-30% of patients with BMs develop epilepsy during the disease course, which is associated with increased morbidity, mortality, and reduced health-related quality of life (HRQoL). Effective seizure management in this population is crucial; however, substantial evidence regarding the efficacy and tolerability of antiseizure medications (ASMs) in patients with BMs is lacking. This study aims to investigate the effectiveness of first-line levetiracetam monotherapy compared to other first-line ASM monotherapies. In this abstract, we present the study protocol and describe the preliminary cohort. MATERIAL AND METHODS We are conducting a retrospective cohort study, collecting data from 1,200 patients with epilepsy due to BMs originating from (non-)small cell lung cancer or melanoma, across eight neuro-oncology centers in the Netherlands. Patients will be matched using nearest-neighbor propensity score matching based on baseline variables potentially influencing ASM choice and study outcomes. A competing risk model will be used to assess the cumulative incidence of treatment failure (for any cause and specific reasons, such as uncontrolled seizures or adverse events), with death as a competing event. RESULTS Until May 2025, data from 347 patients have been collected: 83 (24%) with melanoma, 234 (67%) with NSCLC, and 30 (8.6%) with SCLC. Among them, 232 patients (67%) had a focal first seizure, 104 patients (30%) a focal to bilateral tonic clonic seizure, and in 11 patients (3%), the first seizure type was unknown. As first-line ASM, 321 patients (93%) received levetiracetam, 24 (7%) valproic acid and 2 (1%) carbamazepine. Median overall survival was 14.4 months, ranging from 6.8 months in patients with SCLC to 16.3 months in melanoma, and 17.4 months in NSCLC. At diagnosis, 39% of patients (n=134) had ≥4 BMs, with the largest BM located frontally in 46% (n=160) of cases. Stereotactic radiotherapy (SRT) was administered in 66% (n=230) of patients, as compared to 18% (n=64) receiving whole-brain radiotherapy. Chemotherapy was administered in 127 patients (37%). Sixty-four percent of patients received immunotherapy and/or targeted therapy (n=223). CONCLUSION Epilepsy significantly burdens patients with BMs, yet evidence on the efficacy and tolerability of ASM in this setting remains limited. Findings from this ongoing study may contribute to optimize seizure management and improve outcomes for this patient population.