gms | German Medical Science

71. Jahrestagung der Deutschen Gesellschaft für Neurochirurgie (DGNC)
9. Joint Meeting mit der Japanischen Gesellschaft für Neurochirurgie

Deutsche Gesellschaft für Neurochirurgie (DGNC) e. V.

21.06. - 24.06.2020

EF-14 Phase III post-hoc analysis – TTFields affect tumour growth rates

Post-Hoc Analyse der EF-14 Phase III Studie – TTFields beeinflussen die Tumorwachstumsraten

Meeting Abstract

  • presenting/speaker Adrian Kinzel - Novocure GmbH, Root, Switzerland
  • Noa Urman - Novocure GmbH, Portsmouth, NH, United States
  • Gitit Lavy-Shahaf - Novocure GmbH, Haifa, Israel
  • Shay Levi - Novocure GmbH, Haifa, Israel
  • Ze\'ev Bomzon - Novocure GmbH, Haifa, Israel

Deutsche Gesellschaft für Neurochirurgie. 71. Jahrestagung der Deutschen Gesellschaft für Neurochirurgie (DGNC), 9. Joint Meeting mit der Japanischen Gesellschaft für Neurochirurgie. sine loco [digital], 21.-24.06.2020. Düsseldorf: German Medical Science GMS Publishing House; 2020. DocP012

doi: 10.3205/20dgnc439, urn:nbn:de:0183-20dgnc4399

Published: June 26, 2020

© 2020 Kinzel et al.
This is an Open Access article distributed under the terms of the Creative Commons Attribution 4.0 License. See license information at



Objective: The pivotal EF-14 study on newly diagnosed glioblastoma (nGBM) patients demonstrated that combining TTFields with maintenance temozolomide significantly extends progression-free survival (PFS) compared to temozolomide treatment alone (6.7 vs 4.0 months, p<0.001). It can be hypothesized that TTFields treatment leads to local tumor control and significantly decreased tumor growth rates. In order to test this hypothesis, we analyzed patients from the EF-14 phase III study who received only a biopsy.

Methods: Our analysis included patients from the EF-14 study who received biopsy and showed radiological progression (treatment: N=37/60, control: N=12/29). In a first step, the volumes of the enhancing tumors were segmented on T1c MRIs both at baseline and later at progression. In a second step, we calculated the tumor growth rate as following:

growth_rate=(ln(v0)-ln(v1))/dt. (v0 - tumor volume at baseline), v1 - Tumor volume at progression, dt - days to progression).

This models tumor volume as increasing exponentially over time. Finally, we compared the median growth rates between control and treatment arm.

Results: The calculations demonstrate that the median growth rate was lower in the treatment arm compared to the control (control: 0.14 ± 0.12 mL/month, TTFields -0.011± 0.11 mL/month, p< 0.008 Wilcoxon rank-sum).

Conclusion: Our post-hoc analysis of EF-14 demonstrated that tumor growth rates are reduced in the combined TTFields+TMZ arm when compared to TMZ alone. The analysis only included patients that received a biopsy. The reason for this is that defining the volume of a tumor in resected patients is ambiguous because of the fact that part of the tumor was removed. In summary, our results suggest that TTFields enhances local tumor control.


Stupp R, Taillibert S, Kanner A, et al. Effect of Tumor-Treating Fields Plus Maintenance Temozolomide vs Maintenance Temozolomide Alone on Survival in Patients With Glioblastoma: A Randomized Clinical Trial. JAMA. 2017;318(23):2306-16. DOI: 10.1001/jama.2017.18718 External link
Stensjoen AL, et al. Growth Dynamics of Untreated Glioblastomas in Vivo. Neuro Oncol. 2015 Oct;17(10):1402-11. DOI: 10.1093/neuonc/nov029 External link