Gender, MGMT methylation, and levetiracetam plasma levels correlate with survival benefit in glioblastoma patients treated with adjuvant temozolomide: results from a non-interventional retrospective clinical study

Background: Glioblastoma multiforme (GBM) is a highly aggressive brain tumor, often occurring with seizures. The current standard of care for cancer patients who present seizures includes the use of antiepileptic drugs (AEDs), such as levetiracetam (LEV). Some preclinical studies have shown that LEV may act as histone deacetylases inhibitor (HDACi) through the modulation of O6- methylguanine-DNA methyltransferase (MGMT) expression, thus enhancing temozolomide (TMZ) activity. Methods: In this retrospective, non-interventional clinical study, patients with glioblastoma underwent surgery and radiotherapy and received LEV during adjuvant TMZ chemotherapy. Therapeutic drug monitoring of LEV plasma concentrations was performed through a validated assay using high-performance liquid chromatography (HPLC) with UV-detection, after purification by protein precipitation and solid-phase extraction. The average concentration of the drug throughout follow-up has been related to both patient's clinical characteristics and outcomes. Differences were considered significant at p<0.05. Statistical analysis was performed using the open-source statistical language R (R Foundation for Statistical Computing, Vienna, Austria) through the free and open statistical software program JAMOVI® (Version 1.1.9; retrieved from https://www.jamovi.org). Results: Fourty patients (43% female; mean age = 54.73 ± 11.70 years) were enrolled, and GBM MGMT methylation status assessed. All patients were treated with adjuvant TMZ and LEV to seizures control. While age and TMZ dose (75.17 ± 0.35 mg/m2) did not seem to affect clinical outcomes, median progression-free survival (PFS) was significantly longer in patients harboring methylated MGMT (460 vs. 274.5 days, log-rank p=0.005). Such beneficial effect was more prominent in female (452.5 vs. 216 days, log-rank p=0.026), and in patients whose LEV average concentration was ≤ 25.4 μg/mL (815 vs. 274.5 days, log-rank p=0.003). Moreover, female patients showed a longer overall survival (OS) (1220 vs. 574 days, log-rank p=0.03), and LEV average concentration positively correlated with OS (R = 0.35, p=0.029), too. Female patients without methylated MGMT but treated with higher LEV average concentration ( > 25.4 μg/mL) showed a longer OS with respect to male showing lower LEV average concentration (≤ 5.4 μg/mL), even with (1836 vs. 566 days, log-rank p=0.033) or without methylated MGMT (1836 vs. 324 days, log-rank p=0.019). Conclusion: Female gender and MGMT methylation status may have an impact on PFS and OS of patients with GBM. Nonetheless, where these characteristics are lacking, high plasma concentrations of LEV may succeed with mechanisms not directly involved in controlling epileptic seizures, supporting TMZ effect, and extending patients’ survival