Purser M, Gallagher M, Mladsi D, Weber JM, Andermariam B, Kaye JA, Chawla A. Development of key criteria for an economic model for a potentially curative one-time treatment for sickle cell disease and evaluation of published models with respect to these criteria. Hemasphere. 2020;p.1098-9.

Background: Sickle cell disease (SCD) is a debilitating disease that affects multiple organs and puts patients at lifelong risk for acute events and chronic complications. The development of potentially curative one-time treatments is changing the treatment paradigm. A modeled economic evaluation of such therapies may require a different approach than is used for currently available treatments. Aims To develop key criteria for an economic model for a potentially curative one-time treatment for SCD, and to evaluate previously published models against these criteria.

Methods: Based on a comprehensive review of published studies in SCD (including clinical trials, observational studies, and economic models), we developed key criteria which were then vetted by clinical experts. Eleven published models were identified; 3 pertained to a potentially curative therapy (stem cell transplant). Here, we report evaluation of selected published economic models against these criteria.

Results: A robust model to estimate the economic value of a one-time potentially curative treatment for SCD should consider the following key criteria. Rationale for the key criteria included the following:

1. Heterogeneity in the SCD population (e.g., genotype, sex, age, and extent of organ damage) at time of treatment can lead to differences in disease progression. For example, patients with HbSS/HbSβ° have more rapid decline in kidney function than patients with HbSC/HbSβ+.

2. Treatment options may change over a patient’s lifetime. For example, patients receiving hydroxyurea, after having a stroke, may be switched to chronic transfusions.

3. Trajectories of progression may change over a patient’s lifetime due to a variety of modulating factors. For example, access to care may change due to external healthcare system constraints, such as during the transition from the pediatric to adult care setting for many patients.

4. A potentially curative treatment would result in avoidance of future acute SCD-related events and chronic complications (except preexisting, irreversible organ damage).

5. A modeling approach (e.g., Markov model, patient-level simulation) that accommodates the complexity of the disease is needed. SCD is a highly dynamic condition with many disease states and is becoming increasingly complex with new therapeutic options. Most published economic models in SCD considered only a subset of patients with no consideration of population heterogeneity, a limited time horizon with no consideration of changes in treatment options or progression trajectories over time, and/or only a subset of acute events or complications.

Conclusion: Previously published models are suboptimal for assessing the economic value of a potentially curative treatment. Economic models estimating value of potential curative approaches may require a commensurate modeling approach, which would be distinct from model methodologies applied to-date. A patient-level simulation incorporating heterogeneity in the population at the time of treatment, changes in treatment options over time, and occurrence of time-dependent events influencing future outcomes may be more appropriate than a cohort modeling approach, such as a (memoryless) Markov model.

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