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Cost Per Response Analysis of Strategies for Chronic Immune Thrombocytopenia
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Cost Per Response Analysis of Strategies for Chronic Immune Thrombocytopenia

Kelly Fust, MS; Anju Parthan, PhD; Xiaoyan Li, PhD; Anjali Sharma, MD; Xinke Zhang, MS; Marco Campioni, PhD; Junji Lin, PhD, MS; Xuena Wang, PhD; Richard Zur, PhD; Karynsa Cetin, MPH; Melissa Eisen, MD; and David Chandler, PhD
This decision tree model estimates the cost per response and incremental cost per additional responder for romiplostim, eltrombopag, and “watch and rescue” for immune thrombocytopenia.
ABSTRACT

Objectives: This analysis estimated the cost per response and the incremental cost per additional responder of romplostim, eltrombopag, and the “watch-and-rescue” (monitoring until rescue therapies are required) strategy in adults with chronic immune thrombocytopenia (ITP).

Study Design: The decision tree is designed to estimate the total cost per response for romiplostim, eltrombopag, and watch and rescue over a 24-week time horizon; cost-effectiveness was evaluated in terms of incremental cost per additional responder.

Methods: Model inputs including response rates, bleeding-related episode (BRE) rates, and costs were estimated from registrational trial data, an independent Bayesian indirect comparison, database analyses, and peer-reviewed publications. Costs were applied to the proportions of patients with treatment response and nonresponse (based on platelet count). The total cost per response and the incremental cost per additional responder for each treatment were calculated. Sensitivity analyses and alternative analyses were performed.

Results: With higher total costs and greater treatment efficacy, romiplostim and eltrombopag had a lower 24-week cost per response and a lower average number of BREs than watch and rescue. Eltrombopag was weakly dominated by romiplostim. The incremental cost-effectiveness ratio of romiplostim versus watch and rescue was $46,000 per additional responder. The model results are most sensitive to response rates of romiplostim and watch and rescue and the BRE rate for splenectomized nonresponders. Alternative analyses results were similar to the base case.

Conclusions: In adults with chronic ITP, romiplostim represents an efficient way to achieve response, with lower costs per response than eltrombopag; both romiplostim and eltrombopag had lower costs per response than watch and rescue.

Am J Manag Care. 2018;24(Spec Issue No. 8):SP294-SP302
Takeaway Points
  • Limited evidence evaluating the economic efficiency of thrombopoietin-receptor agonist (TPO-RA) therapy in the United States is currently available in published literature.
  • Results of this analysis provide information on the efficiency (cost per response) and cost-effectiveness (incremental cost per additional responder) of the 2 available TPO-RAs (romiplostim and eltrombopag) and of “watch and rescue” in adults with chronic immune thrombocytopenia in the United States.
  • Romiplostim represents an efficient way to achieve response, with lower costs per response than eltrombopag and watch and rescue.
Chronic immune thrombocytopenia (ITP) is an autoimmune disorder characterized by a low platelet count and increased risk of bleeding. Two thrombopoietin-receptor agonists (TPO-RAs), romiplostim (once-weekly subcutaneous injection)1 and eltrombopag (once-daily oral agent),2 are indicated for the treatment of adults with chronic ITP who have had an insufficient response to corticosteroids, immunoglobulins, or splenectomy.1-4 In clinical practice, patients are sometimes monitored until rescue therapies, like intravenous (IV) immunoglobulin, are required, commonly referred to as the “watch-and-rescue” strategy.

Although some patients undergo splenectomy to treat their ITP, nonsplenectomized patients account for the majority of adult patients with ITP seen by clinical practices in the United States.5 The primary goal of ITP therapy is to help achieve a platelet count that prevents major bleeding.6 Both of the available TPO-RAs have been shown to increase and maintain platelet counts3,4 and reduce the incidence of bleeding-related episodes (BREs). A BRE is defined as the occurrence of a bleeding event and/or use of rescue therapy, including intravenous immunoglobulin (IVIg), anti-D, corticosteroids, platelet transfusions, and dosage increases.7,8 There is limited evidence related to the economics of TPO-RA therapy currently available in published literature.9,10 This analysis was designed to evaluate the cost-effectiveness (in terms of incremental cost per additional responder) and cost per treatment response of the 2 TPO-RAs and the watch-and-rescue strategy for treating adults with chronic ITP in the United States.

METHODS

Overview and Model Structure

The target patient population consists of both splenectomized (51%) and nonsplenectomized (49%) adults with chronic ITP. Model comparators included romiplostim, eltrombopag, and watch and rescue. The model was developed in Microsoft Excel 2010 using Visual Basic for Applications (Microsoft Corp; Redmond, Washington).

The model begins with the decision to treat patients with ITP with either romiplostim or eltrombopag or to adopt the watch and rescue strategy. The analysis was based on a decision tree that stratified patients into response or no response, followed by the presence or absence of a BRE (Figure 1). Costs were applied to each group of patients in the decision tree. The patients were followed over a 24-week time horizon, consistent with the trial durations for romiplostim and eltrombopag.3,4 For each strategy, the average number of BREs, BRE costs, percentage of patients who responded, and total costs, including drug, physician, and lab test costs, were estimated. The total cost per response for each treatment was calculated. Cost-effectiveness was evaluated in terms of incremental cost per additional responder from the US payer perspective.

Treatment Response Rates

Overall platelet response was defined in the romiplostim trials as the percentage of patients with a platelet count ≥50 × 109/L for at least 4 weeks during the trial, excluding responses within 8 weeks after use of rescue medications.3,11 Overall platelet response was defined in the eltrombopag trial as the percentage of patients: (1) with a platelet count of 50-400 × 109/L for at least 4 consecutive weeks during treatment, including all data up to time of withdrawal for patients who prematurely withdrew, excluding responses during rescue treatment and up to the time platelet counts fell below 50 × 109/L after cessation of rescue treatment; or (2) with a platelet count of 50-400 × 109/L for at least 6 of the last 8 weeks of treatment, excluding premature withdrawals and patients using rescue therapy at any time on treatment.11-13 In the model, treatment response was defined by overall platelet response based on the number of weeks with a platelet count ≥50 × 109/L. The response rates for romiplostim were estimated using trial data.3,13 The International Society for Pharmacoeconomics and Outcomes Research (ISPOR) Task Force on Indirect Treatment Comparisons Good Research Practices report suggests that data from head-to-head trials are preferred in economic evaluations of active comparators; in the absence of these data, evidence from an indirect treatment comparison may be considered.14 The results from an independent Bayesian indirect comparison analysis suggested that the overall response rate with romiplostim was significantly higher than with eltrombopag (odds ratio [OR], 0.15).11 Accordingly, the eltrombopag response rates (51.9% for nonsplenectomized and 35.5% for splenectomized patients) were estimated using the romiplostim response rates (87.8% for nonsplenectomized and 78.6% for splenectomized patients) and the OR of 0.15 estimated from Cooper et al.11 The watch-and-rescue response rates for nonsplenectomized and splenectomized patients of 14.5% and 4.8%, respectively, were estimated from pooled placebo response rates.3,4 Response rates are presented in Table 1.1-4,8,11,15-18


 
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