The Impact of Tumor Treating Fields (TTFields) Therapy Usage on Cost-Effectiveness: An Analysis of the Incremental Cost-Effectiveness Ratio (ICER)

OBJECTIVES: Glioblastoma (GBM) is the most common primary central nervous system tumor. It is highly aggressive with a poor prognosis. TTFields therapy has been shown to improve survival in newly diagnosed GBM. In addition, greater daily usage of TTFields therapy by patients has been linked to further improvements in survival. Our objective was to estimate the impact of greater daily TTFields therapy usage on cost-effectiveness, as measured by incremental cost-effectiveness ratios (ICERs).

METHODS: The TTFields therapy Cost-Utility Analysis (CUA) model in Guzauskas et al. was first adapted for the Spanish healthcare system. It was modified to include mortality rates, adverse events (AE), and treatment costs. Overall survival (OS) and progression-free survival (PFS) were modeled using the method in Guzauskas et al. The OS was modeled using a 3-phase approach: (1) EF-14 Kaplan-Meier data up to year 5, (2) Epidemiological long-term conditional survival data from year 5 to year 15, (3) background mortality data from year 15 and beyond. Parametric extrapolation using the Weibull distribution was applied to model PFS curves. OS and PFS data came from patient subgroups of the pivotal EF-14 (NCT00916409) study segmented by daily usage of TTFields, measured in percentage of the day (e.g., 18 hours per day is 75% usage).

RESULTS: Higher daily usage of TTFields therapy was associated with lower ICERs. Daily usage of at least 50% was associated with a decrease of 15% in the ICER, and daily usage of at least 90% was associated with an ICER reduction of 56% compared to the overall trial population. Sensitivity analyses showed that the findings were robust to variations in assumptions about costs and health outcomes related to TTFields therapy.

CONCLUSIONS: This ICER study shows that higher daily usage of TTFields therapy is associated with improved cost-effectiveness, which results from improved clinical efficacy.