Background: Tumor Treating Fields (TTFields) are an anti-mitotic, regional treatment modality, utilizing low intensity alternating electric fields delivered non-invasively to the tumor using a portable medical device. In the EF-14 phase 3 study leading to FDA approval, TTFields significantly extended survival in newly diagnosed GBM when added to maintenance temozolomide (TMZ). Elderly GBM patients usually have worse prognosis and often receive only partial treatment for the disease. The aim of the following post-hoc analysis was to examine the effects of TTFields in the elderly population (≥65 years of age) enrolled in the EF-14 study. Method: All 134 elderly patients (≥65 years of age) from the EF-14's intent-to-treat population were included in the analysis, Overall survival (OS) and progression-free survival (PFS), as well as adverse event frequency and severity were compared between the TMZ + TTFields arm and the TMZ alone arm. Result: The median age was 69 (range: 65-83), 69% were male. Median PFS from randomization was 6.5 months versus 3.9 months in the TTFields + TMZ Vs. TMZ alone arms, respectively (hazard ratio [HR], 0.47 [95%CI 0.30, 0.74] P<0.0236). Median OS was 17.4 months versus 13.7 months in the TTFields + TMZ versus TMZ alone arm, respectively (HR 0.51 [CI 0.33, 0.77] P<0.020). Serious adverse events (SAEs) were reported in 39% of patients treated with TTFields + TMZ and in 33% of patients treated with TMZ alone. None of the SAEs were considered related to TTFields. SAEs were considered related to TMZ or to the underlying disease. Grades 1-2 skin AEs were observed in 51% of patients. Conclusion: Consistent with the overall outcome of the EF-14 study, elderly patients treated with TMZ + TTFields showed significantly better OS compared to patients on TMZ alone, and without increase in grade 3-4 toxicity.

Citation Format: Zvi Ram, Jay-Jiguang Zhu. Efficacy of TTFields in elderly patients with newly diagnosed glioblastoma (GBM): Sub-group analysis of the EF-14 trial [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 CT219.