Assessing the comparative effectiveness of tocilizumab in giant cell arteritis within a de novo health economic model, based on the giacta trial and data from market scan database

OBJECTIVES: To assess the comparative effectiveness of tocilizumab with prednisone vs. prednisone alone, in Giant Cell Arteritis (GCA). METHODS: Ade-novo cost- effectiveness model was built to reflect the natural history of GCA, with the following health states: remission (on and off steroids), relapse/flare and death. A lifetime horizon was applied. Patient's quality of life was estimated using the EQ-5D results from the GiACTA trial. The model accounts for adverse events (AEs) related to prednisone cumulative dose and GCA related AEs with a flare. Time to first flare Kaplan Meier curves were extrapolated using parametric models, rates of subsequent flares were assessed using Poisson regression. Cumulative prednisone dose for each treatment arm was extrapolated in the long run using a logistic regression and linked with probabilities of prednisone related AEs such as diabetes, fractures and serious infections based on the real world data from US MarketScan. RESULTS: In the tocilizumab arm, the median time in steroid free remission was two years longer than patients on prednisone alone. Patients who received tocilizumab had an improved quality of life to those on prednisone alone; this was driven by the reduction in their risk of flare by over 50%. This resulted in a statistically significant (P< 0.0001) decrement over baseline utility, equal to 0.13. Furthermore, patients on tocilizumab reduced their cumulative prednisone significantly, asa result , patients on prednisone alone risk for developing glucocorticoids related AEs are 117% higher than tocilizumab patients. CONCLUSIONS: Tocilizumab significantly improved the quality of life of patients with GCA compared to the current standard of care through more patients achieving better disease control and by reducing the risk of long term AEs.