This is a retrospective study to determine the efficacy of clobazam (onfi) as add-on therapy in brain tumor-related epilepsy (BTRE).A decreased frequency of seizures by more than 50% is used to define clobazam as an appropriate agent to consider for BTRE.

Seizures are common in patients with brain tumors despite antiepileptic treatment. The efficacy of a FDA approved antiepileptic medication, clobazam, has never been evaluated in the context of tumor-related epilepsy although commonly used as add on treatment, often for medically-refractory tumor-related epilepsy.

We retrospectively identified all patients over the age of 18 with a history of BTRE on clobazam over a three-year time span (2016-2019) through the Northwestern University Enterprise Data Warehouse (EDW). Data including patient demographics, clinical notes, health information relating to seizures, concomitant anti-epileptic medications, neurophysiological data, brain imaging, and tumor pathology, was reviewed and entered into the Northwestern University Tumor Related Epilepsy Redcap database and subsequently analyzed for results. 

A total of 32 patients with BTRE on clobazam were identified. Twelve of thirty-two (37.5%) patients achieved >50% reduction in seizure frequency and eighteen of thirty-two (56%) reported seizure freedom after addition of clobazam. Two of thirty-two (6.25%) patients continued to have seizures due to progression of tumor and other medical comorbidities, respectively. The mean effective dose of clobazam was 20.6 milligrams. The mean duration of follow up after addition of clobazam was 15.81 months. Types of tumors seen were glioblastoma multiforme, grade 2-3 astrocytomas and oligodendrogliomas. These were found in the frontal, temporal, parietal and deep structures of the brain. Concomitant anti-epileptics used were clonazepam, diazepam, gabapentin, lorazepam, levetiracetam, lamotrigine, oxcarbazepine, phenytoin, pregabalin, topiramate, valproic acid, zonisamide. 

Our analysis shows clobazam to be an effective agent in BTRE. A comparative study between clobazam and other anti-epileptics in BTRE could be considered in the future.