Phase 1 study of concomitant tumor treating fields and temozolomide chemoradiation for newly diagnosed glioblastoma

Glioblastoma (GBM) is the most common and aggressive primary brain tumor and has limited effective therapies. Tumor treating fields (TTF; Optune Gio^®) is an FDA-approved device with data supporting a significant survival benefit and minimal toxicity when added to maintenance chemotherapy. Uptake in clinical practice is not universal and might improve if a shorter duration of treatment is feasible. This phase 1 trial was designed to determine the safety and preliminary efficacy of TTF concomitant to chemoradiation.

Patients with newly diagnosed, histologically confirmed GBM were eligible. Following surgery, patients were treated with TTF concomitant to standard chemoradiation. The device continued through 2 monthly cycles of maintenance temozolomide with imaging and clinical assessments at regular intervals to assess toxicity and response. The primary endpoint was the safety and tolerability of combined modality treatment based upon the incidence and severity of adverse events. Secondary endpoints were overall survival (OS) and progression-free survival (PFS).

Thirteen patients were enrolled. Dermatologic adverse events were frequent but limited to grade 1/2. There was only 1 serious adverse event possibly related to TTF and no patients were unable to complete the prescribed course of multimodality treatment due to TTF-associated toxicity. Twelve patients were evaluable for median and 6-month progression-free survival which were 8.5 months (mo) and 66.7%, respectively. Median and 12 mo overall survival were 16.0 mo and 83.3%, respectively.

TTF can be safely delivered in conjunction with chemoradiation. The potential for a finite TTF course merits further evaluation.