Tumor treating fields plus temozolomide for newly diagnosed glioblastoma: a sub-group analysis of Korean patients in the EF-14 phase 3 trial

Background Tumor treating fields (TTFields) are anti-mitotic, non-invasive loco-regional cancer therapy comprising low intensity, intermediate frequency alternating electric fields. TTFields plus Temozolomide (TTFields/TMZ) extended survival versus TMZ alone in newly diagnosed glioblastoma (GBM) patients in the EF-14 trial. We report on Korean newly diagnosed GBM patients who participated in the EF-14 trial. Methods Thirty-nine participants of the EF-14 trial were enrolled at 8 sites in South Korea. Patients (24 TTFields/TMZ; 14 TMZ alone) received: TTFields (200 kHz) for > 18 h/day; TMZ at 120-150 mg for 5 days per a 28 day cycle. Safety and efficacy were assessed. Results Patient baseline characteristics were balanced in the 2 arms and the mean age was 52.1 years, 66.7% were male with a mean KPS of 90. Safety incidence was comparable between the 2 arms. In the TTFields/TMZ arm, 30% suffered from skin irritation versus 52% in the entire study population. No TTFields-related serious adverse events were reported. The median progression-free survival (PFS) in the TTFields/TMZ arm was 6.2 months (95% CI 4.2-12.2) versus 4.2 (95% CI 1.9-11.2) with TMZ alone (p = 0.67). Median overall survival was 27.2 months (95% CI 21-NA) with TTFields/TMZ versus 15.2 months (95% CI 7.5-24.1; HR 0.27, p = 0.01) with TMZ alone. Conclusion Median OS and 1- and 2-year survival rates were higher with TTFields/TMZ and similar to the entire EF-14 population. About 30% of patients reported skin irritation, a lower rate than seen in the entire EF-14 population. These results demonstrate the efficacy and safety of TTFields in Korean newly diagnosed glioblastoma patients.