Abstract
BackgroundVoriconazole is well established as standard treatment for invasive aspergillosis (IA). In 2017, isavuconazole, a new antifungal from the azole class, with a broader pathogen spectrum, was introduced in Sweden. A model has therefore been developed to compare the cost-effectiveness of isavuconazole and voriconazole in the treatment of possible IA in adults in Sweden.MethodsThe cost-effectiveness of isavuconazole versus voriconazole was evaluated using a decision-tree model. Patients with possible IA entered the model, with 6% assumed to actually have mucormycosis. It was also assumed that pathogen information would become available during the course of treatment for only 50% of patients, with differential diagnosis unavailable for the remainder. Patients who were considered unresponsive to first-line treatment were switched to second-line treatment with liposomal amphotericin-B. Data and clinical definitions included in the model were taken from the published randomised clinical trial comparing isavuconazole with voriconazole for the treatment of IA and other filamentous fungi (SECURE) and the single-arm, open-label trial and case-control analysis of isavuconazole for the treatment of mucormycosis (VITAL). A probabilistic sensitivity analysis was used to estimate the combined parameter uncertainty, and a deterministic sensitivity analysis and a scenario analysis were performed to test the robustness of the model assumptions. The model followed a Swedish healthcare payer perspective, therefore only considering direct medical costs.ResultsThe base case analysis showed that isavuconazole resulted in an incremental cost-effectiveness ratio (ICER) of 174,890 Swedish krona (SEK) per additional quality adjusted life-year (QALY) gained. This was mainly due to the efficacy of isavuconazole against IA and mucormycosis, as opposed to voriconazole, which is only effective against IA. Sensitivity and scenario analyses of the data showed that the average ICER consistently fell below the willingness to pay (WTP) threshold of 1,000,000 SEK. The probability of isavuconazole being cost-effective at a WTP of 170,000 SEK per QALY gained was 50% and at a WTP of 500,000 SEK per QALY gained was 100%.ConclusionsThis model suggests that the treatment of possible IA with isavuconazole is cost-effective compared with treatment with voriconazole from a Swedish healthcare payer perspective.
Highlights
Voriconazole is well established as standard treatment for invasive aspergillosis (IA)
It was assumed that antifungal treatment was initiated before pathogen information was available to clinicians, and that this information would become available during the course of treatment for only 50% of patients, while differential diagnosis would not be achieved for the remainder
Isavuconazole resulted in 0.3 more quality adjusted life-year (QALY) per patient than voriconazole at an incremental cost of 52,191 Swedish krona (SEK), resulting in an incremental cost-effectiveness ratio (ICER) of 174,890 SEK per additional QALY gained
Summary
Voriconazole is well established as standard treatment for invasive aspergillosis (IA). IFDs such as invasive aspergillosis (IA) or mucormycosis are associated with substantial morbidity and high mortality, especially in high-risk groups [2]. Both IFDs are relatively rare; for example, in an epidemiology study in France, 35,876 patients with IFDs were identified between 2001 and 2010, with an incidence of 1.4 cases/100,000 general population/year for IA and 0.09 cases/100,000 general population/year for mucormycosis [3]. Treatment of IFDs is often initiated before confirmation of the causative pathogen, based on patient risk factors and clinical and radiological signs. Making a differential diagnosis between the two diseases is important, as delaying treatment of mucormycosis by ≥6 days has been reported to substantially increase mortality [10]
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