Abstracts

Rationale: Seizures are a common presenting symptom in patients with oligodendrogliomas, and are often refractory despite multiple antiepileptic drugs (AEDs). Temozolomide chemotherapy can improve seizure (sz) control in patients with oligodendrogliomas. The efficacy of chemotherapy, epilepsy surgery, specific AEDs, and radiation therapy on sz frequency in these patients with medically refractory epilepsy is unknown.Methods: All patients (n=9) with oligodendrogliomas who presented to our epilepsy center between 1988 and 2006 were included in this retrospective analysis. Response to epilepsy surgery, temozolomide, and antiepileptic medications were noted and graded according to sz frequency, averaged over the prior >3 months, at the time of last evaluation after each type of treatment: 1) sz-free, 2) ≥ 80% reduction, 3) ≥ 50% and <80% reduction, or 4) < 50% sz reduction, compared with sz frequency at initial presentation to our center.Results: All 9 patients (mean age 35.7 years, range 10-50 years, 4 men and 5 women) had initial incomplete surgical resections with pathology revealing WHO grade II oligodendrogliomas (2 frontal, 3 fronto-temporal, 2 parietal, 2 parieto-occipital). The mean baseline sz frequency was 11.2 per month (range 3-30 per month), and mean duration of follow-up was 84 months (range 4-84 months). 1 patient received 6 weeks of radiation therapy after initial resection taking valproic acid has been sz-free on topiramate monotherapy for 35 months. 8 patients had epilepsy refractory to ≥2 AEDs (mean 6.0, range 2-14). 6 patients underwent epilepsy surgery, at which time 2 had progressed to WHO grade III. After epilepsy surgery, 1 patient was sz-free (for 41 months), and 1 patient had ≥ 80% reduction in sz frequency after being sz-free for 34 months. 4 patients received temozolomide chemotherapy, 2 of which had evidence of tumor progression on MRI prior to treatment. All of these patients had ≥ 80% sz reduction after temozolomide treatment. Of these, 2 patients had not responded to prior epilepsy surgery. 1 of these patients remains sz-free for 24 months with a prior baseline frequency of daily szs. After treatment with temozolomide, all 4 patients had evidence of tumor stability (mean follow-up of 40.0 months, range 13 months-8 years).Conclusions: Szs can be difficult to control in patients with oligodendrogliomas. These data suggest that chemotherapy can be particularly effective in controlling medically refractory seizures, as well as in stabilizing the tumor on MRI in patients with oligodendrogliomas. Additional studies in larger populations of patients are needed to fully evaluate the roles of chemotherapy, epilepsy surgery, specific AEDs, and radiation therapy for sz control in these patients. The optimal duration of temozolomide therapy for epilepsy is unknown.