Abstract CT061: TRIDENT phase 3 study (EF-32): First-line Tumor Treating Fields (TTFields; 200 kHz) therapy concomitant with chemo-radiation, followed by maintenance TTFields/temozolomide in newly diagnosed glioblastoma

Abstract Background: Tumor Treating Fields (TTFields) therapy is a loco-regional, noninvasive treatment approved for newly diagnosed (nd)/recurrent (r) glioblastoma (GBM) and mesothelioma. Approval for ndGBM was based on the pivotal phase 3 EF-14 study where TTFields therapy/temozolomide (TMZ), administered in the adjuvant setting, significantly improved PFS and OS vs TMZ monotherapy. TTFields therapy-related adverse events (AEs) were mostly mild-to-moderate skin reactions, with no evidence of TTFields therapy-related systemic toxicity. Radiotherapy (RT) concomitant with TTFields therapy demonstrated an increased therapeutic effect in preclinical models. Supplementary evidence from two pilot phase 2 studies demonstrated that concomitant administration of TTFields therapy with standard of care RT/TMZ was feasible and well-tolerated. Here we present a phase 3 study examining the efficacy and safety of TTFields therapy concomitant with RT/TMZ in patients with ndGBM. Materials and Methods: TRIDENT (EF-32; NCT04471844) is a global, randomized, phase 3 study of patients ≥18 years of age (≥22 years in the US) with histologically confirmed ndGBM, ≥3 months life expectancy, ≥70 Karnofsky Performance Status, and adequate organ function. Patients will be stratified by the extent of resection and methylation status of the MGMT promoter. Approximately 950 patients will be assigned 1:1 to continuous TTFields therapy (200 kHz, ≥18 h/day) concomitant with RT/TMZ (experimental arm) or RT/TMZ alone (control arm). Patients will first receive 6 weeks of experimental or control therapy, TTFields therapy will then be added to the control group and all patients will receive 6 cycles of maintenance TMZ and continuous TTFields therapy. Once initiated, TTFields therapy use will continue until second disease progression (PFS2) or until 24 months (if clinically able) from the time of randomization. The primary endpoint is median OS; secondary endpoints include 1- and 2- year OS rates, PFS, 6- and 12-month PFS rates, and PFS2 (all per Response Assessment in Neuro-Oncology [RANO]), overall radiological response (per RANO), severity and frequency of AEs, quality of life (QoL; per European Organisation for Research and Treatment of Cancer QoL Questionnaires), neurological function (per Neurological Assessment in Neuro-Oncology scale), and tumor pathology post study treatments (when available). The ability of TTFields therapy to prolong OS in a dose-dependent manner is an exploratory endpoint. The primary endpoint is based on the hypothesis that TTFields therapy/RT/TMZ can significantly improve OS (vs RT/TMZ) and will be tested using a stratified log-rank test. The sample size is calculated for a hazard ratio of <0.8 with a 5% type I error. The study is expected to enroll patients at 150 sites and is currently open in nine countries. Citation Format: Wenyin Shi, Lawrence Kleinberg, Suriya A. Jeyapalan, Samuel A. Goldlust, Seema Nagpal, Leonardo Lustgarten, Stephanie E. Combs, David Roberge, Ryo Nishikawa, David Reardon, Rachel Grossman, Martin Glas. TRIDENT phase 3 study (EF-32): First-line Tumor Treating Fields (TTFields; 200 kHz) therapy concomitant with chemo-radiation, followed by maintenance TTFields/temozolomide in newly diagnosed glioblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr CT061.

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