HOUSTON – Bronchial thermoplasty has emerged as an important treatment option for patients with severe asthma at specialized centers, Dr. Mario Castro observed at the annual meeting of the American Academy of Allergy, Asthma, and Immunology.
The most recent international European Respiratory Society/American Thoracic Society practice guidelines on severe asthma recommend that bronchial thermoplasty for severe persistent asthma be utilized only in the setting of a clinical study or independent registry. The guidelines cited “very low confidence” in the available estimates of the novel treatment’s longer-term benefits and harms, as well as the lack of data regarding the phenotypes of asthma patients most likely to benefit (Eur. Respir. J. 2014 Feb;43:343-73).
Bruce Jancin/Frontline Medical News
Dr. Mario Castro
Dr. Castro, a member of the task force that developed the ERS/ATS guidelines, said the group’s cautious stance was appropriate given the evidence available at the time of deliberations. However, at the AAAAI meeting, he highlighted more recent study results that address many of the task force’s concerns and that he said might lead to a more enthusiastic recommendation for bronchial thermoplasty in future guidelines.
One key piece of evidence unavailable to the task force comes from results reported in the 5-year prospective follow-up of 162 bronchial thermoplasty-treated patients in the international Asthma Intervention Research 2 (AIR2) trial.
“It’s quite striking that the exacerbation rate did not start to creep back up over time in this severe asthma population. We believe this study shows for the first time that this therapy may actually be a disease modifier, and that you can do this procedure in an identified population and the benefits of this one-time treatment are sustained over at least a 5-year time period,” said Dr. Castro, an AIR2 investigator and professor of pulmonary and critical care medicine and pediatrics at Washington University in St. Louis.
Compared with the baseline established during the year prior to bronchial thermoplasty, at 5 years post procedure, there was a 44% decrease in the percentage of AIR2 participants with severe exacerbations requiring oral corticosteroids, and a 48% reduction in the severe exacerbation event rate. Moreover, there was a 78% reduction in the percentage of patients with an emergency department visit for asthma and an 88% drop in the ED visit event rate (J. Allergy Clin. Immunol. 2013;132:1295-302).
With regard to safety, annual high-resolution CT scans showed no structural abnormalities from baseline to 5 years post-bronchial thermoplasty that could be attributed to the procedure. Prebronchodilator forced expiratory volume in 1 second (FEV1) values remained steady between years 1 and 5 post procedure despite an 18% decrease in the average daily dose of inhaled corticosteroids.
In a separate study, Dr. Castro and coinvestigators at Washington University identified a number of predictors of who will get the best responses to bronchial thermoplasty. This was a small study involving 42 patients with severe persistent asthma as reflected in their baseline mean inhaled corticosteroid dose of 2,185 mcg/day. Eighty percent of patients required bursts of oral corticosteroids during the year prior to the procedure. Their average baseline Asthma Quality of Life Questionnaire (AQLQ) score was 3.42. The baseline FEV1 postbronchodilator averaged 70%, with a range of 44%-121%.
Predictors of a clinically meaningful improvement in quality of life as defined by at least a 0.5-point improvement in AQLQ score 1 year post procedure included a shorter duration of asthma – 19 years, as compared with an average of 45 years in nonresponders – and a greater number of severe exacerbations during the year prior to bronchial thermoplasty.
Using another important yardstick of clinical improvement – at least a 240 mcg/day dose reduction in inhaled corticosteroids or a 2.5 mg/day decrease in oral corticosteroids at 1 year post procedure – significant predictors of benefit included older age (55 vs. 43 years), a lower baseline AQLQ score (2.4 vs. 4.0), and greater need for oral corticosteroids.
In addition, several quantitative metrics obtained through multidetector CT scans of the chest showed promise as predictors of a corticosteroid dose reduction. Responders showed less baseline air trapping, with an average of 6.1% of the lung having a density below –850 Hounsfield units, compared with 12.1% in nonresponders. Responders also had less baseline emphysema-like lung, with 3.2% of the lung having a density below –950 Hounsfield units at total lung capacity, compared with 5.8% in nonresponders, according to Dr. Castro.
This as-yet unpublished study was funded by the National Institutes of Health. AIR2 was sponsored by Boston Scientific. Dr. Castro reported research grants from the NIH, the American Lung Association, Boston Scientific, and other companies.