Abstract LB-155: Adherence to tumor treating fields (TTFields) in high-grade glioma patients - a single center experience
Authors: Hagemann Carsten , Weiland Judith , Lilla Nadine , Linsenmann Thomas , Ernestus Ralf-Ingo , Löhr Mario , Kessler Almuth F. 
Published: August 2019

Abstract
Objective: Therapy with Tumor Treating Fields (TTFields) in combination with adjuvant temozolomide following surgical resection and radiochemotherapy significantly increased survival rates in patients with newly diagnosed glioblastoma (ndGBM) in the phase III trial EF-14. The importance of a high compliance/usage rate was supported by a recently published subgroup analysis, revealing a strong correlation of adherence to TTFields therapy with prolonged overall survival (OS). A compliance rate of 75% and more was demonstrated to be a beneficial independent prognostic factor for OS. Here, TTFields therapy adherence of 36 high-grade glioma (HGG) patients is reported.
Methods: 36 patients diagnosed with HGG received TTFields therapy, amongst them 28 patients diagnosed with GBM and 8 patients with astrocytoma WHO°III. Patients were introduced to the therapy during neurooncologic consultation hours. For assessment of adherence to TTFields therapy, the compliance/usage reports generated at the monthly technical check of the device were analyzed.
Results: At initiation of therapy, the median age of HGG patients was 53.5 years (range 29-67 years). 21 of the 28 GBM patients were diagnosed with ndGBM and the remaining ones had recurrences (rGBM). In these patients, the gender distribution female to male was 1:1.15, which represents a higher ratio of female patients compared to the typical GBM population with 1:1.64. At the time point of data cut-off, ndGBM patients were on TTFields therapy for a median of 6.9 months with a median compliance/usage rate of 84.2%. Regarding therapy adherence, no significant differences were observed between female (84.3%) and male (81.1%) patients. Moreover, comparison between patients with ndGBM and recurrent GBM (rGBM) showed no significant difference in therapy adherence with a median compliance of 71.1% in rGBM patients. For patients diagnosed with astrocytoma WHO°III a compliance rate of 84.5% was reported.
Conclusion: In the reported patients receiving TTFields therapy a high median compliance to TTFields therapy was observed, irrespective of sex and diagnosis. No significant differences regarding the compliance/usage rate was detected between the different groups. TTFields therapy was well accepted by all HGG patients, in particular by female GBM patients. Across all groups, the median compliance/usage rate was substantially above the independent prognostic threshold of 75%. In conclusion, TTFields therapy can be recommended to all eligible patients with HGG.
Citation Format: Carsten Hagemann, Judith Weiland, Nadine Lilla, Thomas Linsenmann, Ralf-Ingo Ernestus, Mario Löhr, Almuth F. Kessler. Adherence to tumor treating fields (TTFields) in high-grade glioma patients - a single center experience [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 LB-155.