10253- ACT-16 OUTCOMES OF MAINTENANCE THERAPY USING TUMOR TREATING FIELDS (TTF) FOR GLIOBLASTOMA AND CHARACTERISTICS FOR CONTINUATION OF TTF MAINTENANCE THERAPY

Abstract BACKGROUND Tumor Treating Fields (TTF) is a novel therapy that inhibits tumor cell division and has been reported to be safe and effective in real-world settings for newly diagnosed glioblastoma in Japan since its insurance coverage in December 2017. This study evaluates the outcomes and characteristics for the continuation of TTF treatment at the Department of Neurosurgery, Tokyo Medical and Dental University. METHODS We retrospectively analyzed adult patients with newly diagnosed supratentorial glioblastoma who completed initial surgery and chemoradiotherapy and began outpatient maintenance therapy between December 2018 and August 2024. Patients were divided into TTF treatment (T group) and non-TTF treatment (N group). The primary endpoints were overall survival (OS) and progression-free survival (PFS), with additional evaluations of patient characteristics and TTF array adherence. RESULTS The study included 49 patients (T group: 14, N group: 35) with a mean age of 66 years (range 25-86). All cases were pathologically diagnosed as glioblastoma (WHO 2016 and 2021). The mean duration of TTF treatment was 282 days (21-1155 days), with a median of 124 days. OS was 837 days (27.9 months) in the T group and 536 days (17.9 months) in the N group (p=0.17), while PFS was 961 days (32.0 months) in the T group and 196 days (6.5 months) in the N group (p=0.012). Long-term TTF users (>=12 months) showed a trend towards extended OS and PFS compared to shorter-term users, with a significantly lower adherence rate at 3 months in early discontinuation cases (p=0.014). CONCLUSION TTF is an effective maintenance therapy for glioblastoma patients, with early high adherence being crucial for its success. Comprehensive patient support, including social aspects, is essential for the continuation of TTF treatment.