Background: Despite attempts to improve the outcome of patients with glioblastoma (GBM), the 3-year survival of patients treated with maximal surgical resection, radiation therapy (RT) and temozolomide (TMZ), followed by maintenance TMZ for 6 months is only 6% with a median OS of 14.6 months. In the EF-14 Phase III trial, the addition of Tumor treating fields (TTFields) at 200 kHz to maintenance TMZ increased the median OS to 20.9 months, compared with 16.0 months with maintenance TMZ alone (HR, 0.63; 95% CI, 0.53-0.76; p< 0.001). Based on these results, the currently accepted standard of care for newly diagnosed GBM (ndGBM) is surgical resection if safely feasible, followed by RT with concomitant TMZ, and then followed by maintenance TMZ in combination with TTFields. Preclinical investigations have confirmed a radio-sensitizing effect of TTFields on glioma cells, suggesting that TTFields given in combination with RT may have a synergistic effect. In a pilot study of 10 patients with ndGBM, we demonstrated that there was no increased treatment-related toxicity when TTFields were given in combination with RT/TMZ. The only TTFields-related adverse event was skin toxicity below the arrays. Preliminary progression free survival (PFS) data was encouraging. Based on the results of the pilot study, we designed this prospective, randomized Phase II study to further investigate if the addition of TTFields TMZ/RT treatment in ndGBM patients improves treatment efficacy and delays disease progression.

Methods: Following debulking surgery or biopsy, 60 adult patients (≥18 years) with histologically confirmed GBM, KPS≥70 and life expectancy of at least 3 months will be randomized 1:1 to either i) RT with concomitant TMZ and TTFields (200 kHz) for 6 weeks followed by up to 6 months of maintenance TMZ in combination with TTFields (experimental arm) up to 24 months; or ii) RT with concomitant TMZ alone followed by maintenance TMZ in combination with TTFields (control arm). Patients with early progressive disease, significant comorbidities precluding maintenance RT or TMZ or patients with an implanted electronic device will be excluded. The primary endpoint is the rate of progression free survival at 12 months (PFS12). Treatment with TTF will be continued until second progression or 24 months (the earlier of the two). All patients will be followed for survival. Grading and severity of all adverse events will be recorded using CTCAE V5.0. The sample size of 60 patients provides 80% power with a two-sided alpha level of 0.05 to detect a PFS12 of 46.5% with RT/TMZ/TTFields compared to 29.4% with RT/TMZ followed, respectively, by maintenance TMZ/TTFields (calculated from the RT/TMZ followed by maintenance TMZ/TTFields arm of the EF-14 trial). It is forecasted to take 24 months to fully recruit. Follow-up will continue for >12 months from recruitment of the last patient.

Citation Format: Rachel Grossman, Dror Limon, Felix Bokstein, Carmit Ben Harosh, Zvi Ram. Randomized Phase II trial of Tumor Treating Fields plus radiation therapy plus temozolamide compared to radiation therapy plus temozolomide in patients with newly diagnosed glioblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr CT203.