Application of tumor treating fields for newly diagnosed glioblastoma: understanding of nationwide practice patterns

Background: Tumor treating fields (TTF) harness magnetic fields to induce apoptosis in targeted regions. A 2015 landmark randomized phase III trial of newly diagnosed glioblastoma (GBM) patients demonstrated TTF + temozolomide to be superior to temozolomide alone. Given these results, we sought to assess practice patterns of providers in TTF utilization for GBM. Methods: A survey was administered to practices in the United States self-identifying as specializing in radiation oncology, medical oncology, neuro-oncology, neurosurgery, and/or neurology. Responses were collected anonymously; analysis was performed using Fisher’s exact test. Results: A total of 106 providers responded; a minority (36%) were in private practice. Regarding case volume, 82% treated at least six high-grade gliomas/year. The provider most commonly certified to offer TTF therapy to GBM patients was the neuro-oncologist (40%), followed by the radiation oncologist (34%); 31% reported no TTF-certified physician in their practice. TTF users were more likely to have high volume, and be aware of TTF inclusion in National Comprehensive Cancer Network (NCCN) guidelines (p < 0.05). Conclusions: More than 80% of TTF for GBM in the United States is performed by groups who treat at least six high-grade gliomas per year; unfortunately more than 30% were in practices bereft of anyone certified to offer TTF therapy. These results indicate that there remains fertile soil for TTF therapy nationwide to be introduced into practices for GBM treatment. Providers seeking to refer newly diagnosed GBM patients for TTF should seek out practices with TTF user-associated characteristics to ensure optimal access for their patients.