Introduction: Glioblastoma multiforme (GBM) is the most common malignant primary intracranial tumor and traditionally has a median survival of only 10 to 14 months, with only 3 to 5% of patients surviving more than three years. Recurrence is nearly universal, and further decreases the median survival to only 5 to 7 months with optimal therapy. Tumor treating fields (TTFields; Optune, Novocure, Haifa, Israel) therapy is a novel treatment technique that has recently shown significant prolonged survival in GBM patients. This therapy is approved for the treatment of newly diagnosed and recurrent GBM and is based on the principle that low intensity, intermediate frequency alternating electric fields (100 to 300 kHz) have an anti-mitotic effect in specific cell types. The applied fields disrupt the mitotic spindle, microtubule assembly and the segregation of intracellular organelles during cell division, leading to apoptosis or mitotic arrest. We aimed to compare overall survival between patients treated with standard therapy and standard therapy plus TTFields at our institution.

Materials and Methods: A total of 34 patients (22 male, 15 female) diagnosed with GBM and treated by standard therapy plus TTFields (STDTh-TTF) at our institution were included. Standard therapy (STDTh) consisted of surgical resection, followed by combined radiotherapy and chemotherapy (Temozolomide); in 2 cases biopsy was performed in place of resection. The date of resection or biopsy was considered the entry date and was used in calculating survival, and ranged from June 2015 to July 2019. A matching control group treated by STDTh alone at our institution was assembled from our database, based primarily on date of resection or biopsy, and secondarily by age (1 subject underwent biopsy in place of resection). When assembling the control group, the investigators were blinded to survival outcome.

Results: Significantly greater overall survival was observed for the group treated by TTFields in addition to standard therapy (p = 0.005; Hazard ratio [HR] 0.28; 95% confidence interval [CI] 0.11-0.69). The groups were identical with respect to sex, and no differences with respect to age (p=0.12; STDTh-TTF mean 50.54 years, SD 10.3; STDTh mean 54.39 years, SD 9.3) or inclusion date (p=0.3) were detected.

Conclusions: Our initial results appear promising with respect to overall survival in patients undergoing TTFields treatment in addition to standard therapy.

Citation Format: Aaron Rulseh, Adam Derner, Jan Sroubek, Jan Klener, Josef Vymazal. Overall survival of glioblastoma patients treated by standard therapy in comparison to standard therapy plus tumor treating fields [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2038.