By Joe Zein, MD, Sumita Khatri, MD, and Belinda Udeh, PhD, MPH
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Bronchial thermoplasty (BT) was approved by the Food and Drug Administration (FDA) in 2010 based on clinical trials demonstrating its effectiveness. Patients with severe persistent asthma are eligible if they are at least 18 years old and their asthma is not well-controlled with inhaled corticosteroids and long-acting beta-agonists. However, the cost-effectiveness of this procedure in treating this patient population remains uncertain.
To further explore this question, we analyzed data using a Markov decision analytic model to estimate the cost effectiveness of BT as compared with usual care. We abstracted our baseline case characteristics from the AIR2 trial (Asthma Intervention Research 2), the only randomized controlled trial published to date.
Although only five-year outcomes data are available from the clinical trial, clinical effectiveness of BT is expected to last beyond five years. We explored the value of BT over a 10-year period after treatment. Further, we assumed the effect of BT remained constant for the first five years, in line with current clinical trial data, and then conservatively estimated that its clinical effect would decrease at a rate of 20 percent for every subsequent year over the next five years. The main outcome measure was cost in 2013 dollars per additional quality adjusted life year (QALY).
We found that treatment with BT resulted in 6.40 QALYs and $7,512 in cost compared with 6.21 QALYs and $2,054 for usual care. The incremental cost-effectiveness ratio (ICER) for BT at 10 years was $29,821/QALY. At five years, BT remained cost-effective with an ICER of $45,300/QALY. At both time points, the cost/QALY fell below the society “willingness to pay” benchmark of $50,000/QALY.
We also conducted sensitivity analysis to assess the combined effect of all uncertainties on the model and to explore the results within the context of population variability. At a society willingness to pay per QALY of $50,000, BT continues to be cost-effective unless the probability of severe asthma exacerbation drops below 0.63 exacerbation per year or the cost of BT rises above $10,384 total for the complete BT treatment (consisting of three separate bronchoscopic procedures).
Thus, our findings suggest that the cost-effectiveness of BT depends mostly on the probability of asthma exacerbation in the usual care group and on the procedure cost (Figure). To be cost-effective, BT should be used in patients with high asthma exacerbation rates but clinical capacity to safely tolerate BT.
Finally, the cost-effectiveness of BT drops with older patient age due to higher background mortality. Our model population was based on the patient demographics listed in the AIR2 trial with the cohort entering the simulation at age 41, the mean age of the AIR2 trial population. Therefore, the ICER for BT at 10 years of $29,821/QALY cannot be generalized to an older patient population. In that regard, the ICER for BT becomes $157,227 per QALY for individuals who are 65, suggesting that BT may not be cost-effective for older patients with asthma.
Based on our findings, we recommend using BT for younger patients meeting the FDA indication criteria who are at high risk of asthma exacerbation. Continuing to follow beyond five years patients whose severe asthma has been treated with this relatively new procedure will aid the further evaluation of its long-term cost-effectiveness.