Abstracts

Rationale: Levetiracetam (LEV) monotherapy for partial seizure (monoTx) is reported to be safe and effective, but no studies address its use during gamma knife surgery for brain tumors (GK). Phenytoin (PHT) treatment of seizures in this population is standard, however, new AEDs are attractive in patients with neoplasms requiring chemotherapy and glucocorticoids due to less drug interactions, tolerability, and less CYP450 induction. This study compares efficacy and tolerability of LEV and PHT monoTx in GK patients.Methods: We retrospectively reviewed the Hoag Gamma Knife Program database from January 2004 through January 2006. Seizure frequency, side effects, and blood draws are routinely documented for all patient encounters. Men and women aged 16-90 years on LEV or PHT monoTx were included. Chart review included: (a) seizure frequency, rated as seizure free, few seizures (no generalized tonic clonic (GTC) and ≤ two partial seizures/ month), or severe seizures (any GTC, or ≥ three partial seizures/ month); (b) presence or absence of side effects or reactions; (c) number of blood draws for AEDs; and (d) Karnofsky Performance Scale (KPS) score. Statistical analysis was utilized to determine differences between groups.Results: We identified 80 patients on PHT monoTx and 32 patients on LEV monoTx with a mean age of 57.7 years. Pathology included metastatic tumor (56% of PHT and 59% of LEV), glioblastoma (24% of PHT and 16% of LEV), astrocytoma (7% of PHT and 19% of LEV) and meningioma (13% of PHT and 6% of LEV). (a) No differences in seizure control were seen, with 81.3% of PHT and 84.4% of LEV seizure free, 15.0% of PHT and 15.6% of LEV with few seizures, and 3.8% of PHT and 0 % of LEV with severe seizures. (b) 53.1% of LEV and 28.8% of PHT reported side effects (Fisher’s Exact Test, p-value = 0.018; Mann-Whitney U test, p = 0.015). Common side effects were: headache (30.3% LEV and 13.9% PHT), somnolence (18.2% LEV and 3.8% PHT), and ataxia (3% LEV and PHT). Rash led to AED discontinuation, but was uncommon (0 % LEV and 5% PHT). (c) Mean blood draws performed per patient were higher for PHT (1.84, range 0-5, sd = 1.02) versus LEV (0.06, range 0-1, sd = 0.2), (Mann-Whitney U test, p = 0.00). (d) Mean KPS scores in PHT (82.4) and LEV (78.8) did not differ.Conclusions: LEV monoTx was no less effective than PHT monoTx in controlling seizures in patients undergoing GK for a variety of brain tumors. No differences occurred in KPS scores. In contrast to previous studies, a higher percentage of LEV patients reported side effects, which may represent a special concern in the GK population. Inclusion of headache, a known side effect of LEV, may have confounded this result as headaches are common in patients with brain tumor. Larger, prospective studies are needed. The only serious adverse reactions (rash) leading to AED discontinuation occurred in PHT monoTx. Blood draws were more frequent in PHT monoTx, increasing service utilization. Compared with PHT monoTx, LEV monoTx for seizure treatment and prophylaxis in GK was effective, safe, and associated with fewer blood draws.