Abstract LB-160: Glioblastoma and mesothelioma: Do estimates of health state utilities compare in rare cancers treatable with tumor treating fields

Objective: To compare the estimated health state utilities of glioblastoma (GBM) and malignant pleural mesothelioma (MPM) given that they are both rare cancers treatable with tumor treating fields (TTFields) Background: Glioblastoma (GBM) is the most aggressive form of primary brain cancer in adults. MPMis an invasive and generally fatal malignancy of the lung mainly caused by exposure to asbestos fibers. To understand the comparative economic value of new treatments, the quality-adjusted life year (QALY) has been developed and is widely used in health economic literature. Given that GBM and MPM are both rare and aggressive cancers, both potentially treatable with TTFields, we aimed to understand whether the estimated health state utilities for each disease state were comparable. Clinical results show a comparable effect on median overall survival (OS). The EF-14 Trial showed that the addition of TTFields treatment increases median OS by 4.9 months in GBM, while the EF-23 showed that TTFields adds a median OS of 6.1 months compared to historical control in MPM. Differing health state utilities by disease, in this case a central nervous system tumor versus a pleural tumor, could influence the adoption of a new treatment regardless of whether the efficacy and safety of that new treatment is comparable for both disease states. Methods: We reviewed the structure and results of the EF-14 and STELLAR trials. We determined the appropriate health states for evaluation in both diseases as stable disease, progressed disease, and death. We then performed a comprehensive review of the published literature regarding health utility values in GBM and MPM patients using a boolean search in the Medline database. The estimated health state utilities were then compared by disease. Results: All publications that reference health utilities for GBM are derived from the same source. Estimates of utility were obtained from the NHS Value of Health Panel (VoHP) and based on the standard gamble method for preference elicitation, rating a total of nine descriptive health state scenarios. Utilities for stable disease in glioblastoma were 0.85 and 0.73 for progressed disease as a base case respectively. The estimates for MPM utilities were obtained using varying methods not correlated to stable or progressive disease. One method elicited utilities describing 243 distinct states from the EQ-5 questionnaire data collected during the trial at an indiviual patient level. Conclusions: Health utility estimates published so far for GBM are not comparable to the helth utilities published and used for MPM. While the utilities in GBM are scarce, but allow for use in a three health state disease model, utilities for MPM are more diverse and do at the moment not support a health state model. MPM utilities elicited from the EQ-5 however describe more adequately the individual utilities and their change during the course of the disease. The lack of such detailed utilities e.g. in GBM could lead to disparities in the assessment of cost effectiveness of new treatments like tumor treating fields for different indications, despite similar costs and clinical efficacy. Citation Format: Christina Proescholdt, Justin Kelly. Glioblastoma and mesothelioma: Do estimates of health state utilities compare in rare cancers treatable with tumor treating fields [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-160.