10164-CS-16 Early Combination of Bevacizumab and Tumor Treating Fields in Glioblastoma Patients with Unresectable Tumors or Poor Performance Status

Abstract Background The early combination of radiation therapy and temozolomide (RT+TMZ), bevacizumab (BEV), and tumor treating fields (TTFields) for newly diagnosed glioblastoma (GBM) has not been previously reported. In Japan, BEV is approved for the treatment of newly diagnosed GBM, and its early administration may facilitate TTFields initiation in patients with poor performance status (PS) or unresectable tumors by improving PS. Methods We retrospectively analyzed 12 patients with newly diagnosed GBM treated with early BEV in combination with RT+TMZ, followed by TTFields, between October 2018 and March 2024. As a control group, we evaluated 25 patients who received standard RT+TMZ without early Bev, followed by TTFields. Results There were no significant differences in age, sex, or MGMT methylation status between the groups. However, the early BEV group had a significantly lower preoperative KPS (median 70 vs. 80, p = 0.031) and a lower GTR+STR rate (p = 0.028), indicating a poorer baseline condition. In the early BEV group, patients with a KPS of 60 or lower showed improvement to 70 or higher before the initiation of TTFields following BEV administration. Median progression-free survival (PFS) was 10.2 months in the early BEV group and 16.1 months in the standard RT+TMZ group (p = 0. 58). Median overall survival (OS) was not reached in the early BEV group and was 23.5 months in the standard RT+TMZ group (p = 0. 48). Dermatitis was common in both groups, but BEV did not worsen TTFields-related skin toxicities, and no wound healing delay was observed. Conclusion In newly diagnosed GBM patients with unresectable tumors or poor PS, early BEV administration improved PS and enabled the introduction of TTFields. Further validation with a larger cohort and prospective studies is warranted.