The first study to follow up asthma patients treated with bronchial thermoplasty beyond five years has shown that the benefits persist for at least a decade, and the procedure has an acceptable safety profile.
Patients with severe uncontrolled asthma who participated in three key randomised controlled trials conducted before 2010 have been followed up by researchers to see if the early benefits of the procedure were maintained.
The BT10+ study investigators were able to locate about half (45%) of the original 429 participants enrolled in the AIR, RISA, and AIR2 trials for a follow up visit to assess asthma outcomes and imaging to look for changes such as bronchiectasis.
They found that at follow up of 11-16 years (median 12·1 years) after bronchial thermoplasty, the primary efficacy outcome of severe exacerbation in the previous 12 months was similar (25%) to rates seen in the first year (24%) and fifth years (22%) after treatment .
The effect of thermoplasty on hospital emergency department visits was also maintained at the ten year visit, while quality of life measurements and spirometry were also similar between year one, five and the 10+ years visit.
CT imaging showed no evidence of any bronchostenosis, or interstitial CT abnormality after bronchial thermoplasty, but bronchiectasis developed in six (7%) of 89 participants treated who did not have at baseline. All but one of the cases of bronchiectasis was classified as mild, and not accompanied by clinical correlates such as cough, sputum, or recurrent infection.
Writing in Lancet Respiratory Medicine, the study investigators acknowledged that their findings were limited because less than half the original trial patients were still available for review, but noted that the clinical characteristics of those traced were the same as those lost to follow-up, both at the baseline evaluation and at 12-month post-treatment follow-up.
They said it was reassuring that there appeared to be no safety concerns such as increased asthma deaths among those who underwent bronchial thermoplasty, and also notable that there was no apparent progressive decline in lung function over ten or more years, as would be expected with age.
Due to the design and small sample size of the original trials it was not possible to identify whether any particular subsets of patients were more likely to respond to bronchial thermoplasty in the long term.
However, there seemed to be better responses for patients who had more bronchial thermoplasty treatments (activations), for younger patients and those with higher baseline lung function or worse asthma quality of life scores.
“Long-term (>10 years) evidence suggests that bronchial thermoplasty is a safe and effective non-pharmacological therapy for asthma, and can be considered as a treatment option for patients whose asthma remains uncontrolled despite optimised medical therapy,” they concluded.
Associate Professor David Langton of the Department of Thoracic Medicine, Frankston Hospital, Victoria, said the findings might address some of the concerns around a procedure that is still regarded with caution by many respiratory specialists because it was irreversible.
In an accompanying commentary, he said it remained to be seen whether the bronchiectasis seen at ten years follow up was due to bronchial thermoplasty, or whether it would have occurred as part of the natural history of asthma in these patients.
“However, there is mounting evidence that bronchial thermoplasty exerts part of its physiological effect by causing dilatation of treated airways, and it is possible that this is what was observed in the imaging,” he wrote.
He also noted that unlike when the trials were conducted, patients with uncontrolled severe asthma now have access to monoclonal antibody therapies.
“However, patients with Th-2 low asthma have been left behind in the rush, for whom only macrolide therapy has shown promise, and only then in short-term studies. Bronchial thermoplasty shows its greatest application in such patients. This study … provides both hope and reassurance for these patients and their clinicians,” he concluded.
Disclosure: Some of the article authors declared receiving grants from Boston Scientific, which makes the Alair thermoplasty system. Associate Professor David Langton declared no interest.