Abstracts

Rationale: Epilepsy is a common complication in patients with primary CNS tumors and has a major impact on clinical management. Approximately 30% of all patients with brain tumors develop epilepsy, reaching as high as 80-90% for those with low-grade gliomas. Tumor-related epilepsy has significant long-term effects on neurocognitive function and quality of life. Thus, effective seizure control for patients with tumor-related epilepsy is a key issue for clinicians to improve patient outcomes. Unfortunately, despite medical management 12-50% of patients will become medically refractory depending on the tumor type. There is currently limited data predicting which patients will become refractory to anti-epileptic medications (AEDs). Thus, the goal of this study was to determine factors which could predict which patients will develop refractory epilepsy.  Methods: This was a retrospective chart review including 53 patients selected from the neuro-oncology clinic at Northwestern Memorial Hospital over a 6-month period. The main inclusion criteria were the diagnosis of a primary CNS brain tumor and tumor-related epilepsy. Patient's charts were reviewed between 0 and 12 months after initiation of first and second line anti-epileptic agents assessing for AED failure. AED failure was defined as the need to add an additional AED due to inadequate seizure control. Refractory epilepsy was defined as AED failure of more than 2 medications with continued uncontrolled seizures. Patient's charts with refractory epilepsy were then used to collect information about the CNS tumor type/location, molecular genetics, surgical/medical treatment of tumor, seizure semiology/frequency, and antiepileptic medications.  Results: First and second line AEDs included levetiracetam, lacosamide, lamotrigine, oxcarbazepine, phenytoin, and valproic acid. There was a 47.1% AED failure rate observed for 1st line agents, and a 47.3% AED failure rate for patients started on 2nd line agents. Refractory epilepsy was seen in 13.2% of patients. After the initiation of first line AED, 85.7% of patients who developed refractory epilepsy had seizure freedom intervals of <1 month. 90% of patients who did not develop refractory epilepsy had seizure free intervals >1 month. There were no differences observed between those who developed refractory epilepsy compared to those who did not with regards to tumor type/location, genetic markers (i.e methylation status, IDH status), seizure semiology/frequency, or anti-epileptic medication.  Conclusions: The only significant factor predicting the development of refractory epilepsy in this study was the length of seizure freedom period after initiation of first line AED, with seizure free intervals less than 1 month having a much higher risk for refractory epilepsy. Additionally, there was also no statistical difference in efficacy between the 1st and 2nd line anti-epileptic medications in tumor-related epilepsy. Funding: No funding