Abstract CT205: Tumor Treating Fields alters progression patterns in glioblastoma: An imaging analysis of the EF-14 Phase III trial

Introduction: Tumor Treating Fields (TTFields) are alternating electric fields delivered via transducer arrays placed on the scalp The EF-14 [NCT00916409] trial showed improved survival outcomes in newly diagnosed Glioblastoma (GBM) patients treated with TTFields plus Temozolomide (TMZ) versus TMZ alone We analysed EF-14 data to test the hypothesis that because TTFields delivery is planned to optimize dose at the tumor bed: TTFields treated patients are more likely to exhibit distal progressions, including progression to the infratentorium, the region where TTFields dose is minimal when planning treatment to target primary tumors in the supratentorium Tumor growth rates are slower in patients treated with TMZ+TTFields Methods: Patients on treatment for more than two months who exhibited radiological progression were included in the study (treatment: N=280/466, control: N=122/229) Regions of enhancing tumor, necrosis and resection were contoured on T1 contrast MRIs taken at baseline and at the date of first progression reported by the treating center Progressions were classified into three groups: Local progressions: 3 mm from the original tumor or resection cavity; Combined local and distal progressions: both local and distal progressions were visible The growth rate of the tumor was estimated and the distance between the original lesions and new distal lesions was measured Patients with (distal) infratentorial progression were identified. Results: More cases of non local (distal or combined local and distal) progression were observed in the treatment arm The difference between the groups was not statistically significant (69/280 vs 23/122 P Conclusions: This imaging analysis of the EF-14 Phase III trial demonstrates that adding TTFields to TMZ has substantial impact on GBM growth patterns and rate In addition to prolongation of survival times during TTFields treatment, this is another validation for the local efficacy of TTFields therapy TTFields increases local control of tumor growth, emphasizing the need for adaptive treatment after progression to control progressing disease Further studies are needed to elucidate the association between progression and TTFields dose distributions. Citation Format: Suriya Jeyapalan, Steven A. Toms, Andreas Hottinger, Lawrence Kleinberg, Erqi Pollom, Scott G. Soltys, Martin Glas. Tumor Treating Fields alters progression patterns in glioblastoma: An imaging analysis of the EF-14 Phase III trial [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr CT205.