Abstract
Background
The subgroup of patients age 65 and older showed the the greatest survival benefit from TTFields plus TMZ treatment in the EF-14 trial (hazard ratio 0.51 [CI 0.33–0.77]). This is the first report on the cost-effectiveness of adding TTFields to the maintainance phase of the first line treatment protocol for elderly GBM patients from a U.S. health system perspective.
Material and Methods
The endpoint of this analysis was the projected incremental cost-effectiveness ratio (ICER) of adding TTFields to the standard-of-care for newly diagnosed GBM in the maintenance phase of treatment for patients over 65 years of age. Patient outcomes were simulated using a 3-state area under the curve model including alive with stable disease, progressed disease, and death. Survival was modelled over a lifetime horizon by integrating the 5-year survival results for elderly patients reported in the EF-14 trial with long-term GBM epidemiology data and U.S. background mortality rates. Data on patient utilities used to calculate quality-adjusted life years (QALYs) were based on a previous analysis of GBM-specific health-state preferences. Frequency of adverse events associated with TTFields and TMZ were derived from the EF-14 trial for the patients over 65 years. Costs for adverse events and supportive care cost estimates were used according to published literature. Future survival benefits and costs were discounted to present value at a rate of 3%. One-way and probabilistic sensitivity analyses were performed to assess result uncertainty due to parameter variability.
Results
Patients treated with TTFields and maintenance TMZ achieved mean lifetime survival of 3.66 years before discounting and 3.04 years after discounting future survival. Patients treated with TMZ alone achieved a mean lifetime survival of 1.32 years without discounting and 1.29 years after discounting future survival. The resulting incremental life years gained were 1.75 years after discounting future survival benefits, andthe incremental quality-adjusted life years (QALYs) were 1.35. The incremental total cost was $192,000. The ICER was $109,500 per LYG and $142,400per QALY gained. The probability of TTFields being cost-effective was 85% at a willingness-to-pay threshold of $200,000 per QALY.
Conclusion
Treating newly diagnosed GBM patients over 65 years of age with TTFields and TMZ has the potential to increase mean lifetime survival and quality-adjusted survival substantially compared to treatment with TMZ alone. TTFields therapy, even when evaluated at its full list price, demonstrated a high probability of cost-effectiveness at willingness-to-pay thresholds reported in economic literature for the United States. These results indicate that patients over age 65 may not only benefit from TTFields treatment more than other subgroups, but also that their treatment may be more cost-effective.