Seizures as treatment-emergent adverse events during glioblastoma clinical trials.

e14018 Background: Seizures are not an uncommon presenting symptom of glioblastoma (GBM), and may occur following surgery for GBM. Such seizures typically can be controlled with anti-epileptics, and the risk of seizures seems to decrease after concurrent radiation therapy and temozolomide chemotherapy (RT/TMZ). However, the risk of seizures theoretically might be increased in association with a therapeutic intervention designed to enhance local inflammation at the GBM site. 33% of patients experienced one or more seizures as a treatment-emergent-adverse-event (TEAE) during a phase II clinical trial of AV-GBM-1, patient-specific dendritic cell vaccines that consist of autologous dendritic cells loaded with autologous tumor associated antigens derived from a short-term culture of self-renewing tumor cells, that were injected subcutaneously for up to six months after recovery following concurrent RT/TMZ (Bota DA et al. 2021 Society for Immunotherapy of Cancer (SITC) late-breaking abstract #952, 2021 Society of Neuro-Oncology abstract #CTIM-33). A literature search was conducted to determine reported rates of seizures as TEAE in primary GBM patients in clinical trials. Methods: Phase III trials of systemic treatment of primary GBM, and published during 2005 to 2021, were identified by searches of clinicaltrials.gov and PubMed. Published reports were reviewed for data describing the frequency of seizures reported as TEAE in text and/or summary tables. Only trials that had at least 50 patients in a standard treatment arm of surgical resection, RT/TMZ and maintenance TMZ were included. Chi square test was used to compare proportions of patients experiencing seizures in these trials. Results: Eight such randomized trials were identified. Five trials did not mention seizures as TEAE. One trial provided data only for grade 3 and 4 events: 13/229 (5.7%). The other two trials reported all seizures regardless of grade, but were limited to patient populations with O6-methylguanine-DNA-methyltransferase promoter methylation in one, and epidermal growth factor receptor amplification in the other. The rates of seizures in those two trials were much lower than the 19/57 (33.0%) reported with AV-GBM-1: 28/258 (10.9%, p < 0.0001), and 69/372 (15.4%, p = 0.0136). Conclusions: The frequency of seizures that occur in GBM patients receiving standard RT/TMZ is not well-documented in publications of large, randomized trials. AV-GBM-1 may be associated with a higher rate of seizures because of treatment-induced inflammation at the tumor site, but a randomized trial would be needed to determine this.