(OA14) Application of Tumor Treating Fields for Newly Diagnosed Glioblastoma Multiforme: Understanding of Nationwide Practice Patterns and Trends

Abstract

Tumor treating fields (TTF) are a low-intensity, intermediate-frequency, non-invasive and regional anti-mitotic treatment that harnesses magnetic fields to induce apoptosis in targeted regions. A Food and Drug Administration-approved TTF system demonstrated a significant increase in survival of newly diagnosed glioblastoma multiforme (GBM) in 2014. One year later, in a landmark randomized phase III trial of newly diagnosed GBM patients, TTF + temozolomide demonstrated superiority to temozolomide alone. Given these findings, we sought to assess practice patterns and trends of providers in the utilization of TTF for GBM. A survey designed through the Oregon Clinical and Translational Research Institute was administered to practices in the United States which self-identified as specializing in radiation oncology, medical oncology, neuro-oncology, neurosurgery, and/or neurology. Responses were collected anonymously; the survey was constructed to assess responder knowledge of appropriate clinical scenarios for TTF, knowledge of TTF therapy status on National Comprehensive Cancer Network (NCCN) guidelines, and personal approaches for patients with recurrent GBM, as well as additional demographic data. A total of 106 providers responded; 95% were practicing physicians representing Missouri (8.9%), Massachusetts (7.9%), California (6.9%), Philadelphia (5.9%), Oregon (5.9%), and Illinois (5.9%). The most common responders were radiation oncologists (75%) and neuro-oncologists (22%); medical oncologists (3%) and neurosurgeons (1%) comprised the remaining responders. The average number of physician-partners in a responder’s practice group was 7.6; a minority (36%) were in private practice. With regard to case volume, only 18% treated 0-5 high-grade gliomas per year, while 24% treated 6-10 annually, and 58% treated at least 10 high-grade gliomas annually. The provider most commonly reported as certified to offer TTF therapy to GBM patients was the neuro-oncologist (40%), followed by the radiation oncologist (34%); 31% reported no physician in their practice being certified to offer TTF therapy. The vast majority of TTF for GBM in the United States is administered by neuro-oncologists and radiation oncologists, usually in an academic setting involving 7-8 physician-partners. More than 80% of TTF is performed by groups who treat at least six high-grade gliomas per year. However, one-fifth of providers were unaware of TTF therapy being listed on current NCCN guidelines for GBM treatment, and 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. Given the promising results of TTF for GBM in clinical trials thus far, this opportunity should be seized energetically.