Bronchial thermoplasty for moderate or severe persistent asthma in adults

Background Bronchial thermoplasty is a procedure that consists of the delivery of controlled radiofrequency-generated heat via a catheter inserted into the bronchial tree of the lungs through a flexible bronchoscope. It has been suggested that bronchial thermoplasty works by reducing airway smooth muscle, thereby reducing the ability of the smooth muscle to bronchoconstrict. This treatment could then reduce asthma symptoms and exacerbations, resulting in improved asthma control and quality of life. Objectives To determine the efficacy and safety of bronchial thermoplasty in adults with bronchial asthma. Search methods We searched the Cochrane Airways Group Specialised Register of Trials (CAGR) up to January 2014. Selection criteria We included randomised controlled clinical trials that compared bronchial thermoplasty versus any active control in adults with moderate or severe persistent asthma. Our primary outcomes were quality of life, asthma exacerbations and adverse events. Data collection and analysis Two review authors independently extracted data and assessed risk of bias. Main results We included three trials (429 participants) with differences regarding their design (two trials compared bronchial thermoplasty vs medical management and the other compared bronchial thermoplasty vs a sham intervention) and participant characteristics; one of the studies included participants with more symptomatic asthma compared with the others. The pooled analysis showed improvement in quality of life at 12 months in participants who received bronchial thermoplasty that did not reach the threshold for clinical significance (3 trials, 429 participants; mean difference (MD) in Asthma Quality of Life Questionnaire (AQLQ) scores 0.28, 95% confidence interval (CI) 0.07 to 0.50; moderate-quality evidence). Measures of symptom control showed no significant differences (3 trials, 429 participants; MD in Asthma Control Questionnaire (ACQ) scores -0.15, 95% CI -0.40 to 0.10; moderate-quality evidence). The risk of bias for these outcomes was high because two of the studies did not have a sham intervention for the control group. The results from two trials showed a lower rate of exacerbation after 12 months of treatment for participants who underwent bronchial thermoplasty. The trial with sham intervention showed a significant reduction in the proportion of participants visiting the emergency department for respiratory symptoms, from 15.3% on sham treatment to 8.4% over 12 months following thermoplasty. The trials showed no significant improvement in pulmonary function parameters (with the exception of a greater increase in morning peak expiratory flow (PEF) in one trial). Treated participants who underwent bronchial thermoplasty had a greater risk of hospitalisation for respiratory adverse events during the treatment period (3 trials, 429 participants; risk ratio 3.50, 95% CI 1.26 to 9.68; high-quality evidence), which represents an absolute increase from 2% to 8% (95% CI 3% to 23%) over the treatment period. This means that six of 100 participants treated with thermoplasty (95% CI 1 to 21) would require an additional hospitalisation over the treatment period. No significant difference in the risk of hospitalisation was noted at the end of the treatment period. Bronchial thermoplasty was associated with an increase in respiratory adverse events, mainly during the treatment period. Most of these events were mild or moderate, appeared in the 24-hour post-treatment period, and were resolved within a week. Authors' conclusions Bronchial thermoplasty for patients with moderate to severe asthma provides a modest clinical benefit in quality of life and lower rates of asthma exacerbation, but no significant difference in asthma control scores. The quality of life findings are at risk of bias, as the main benefits were seen in the two studies that did not include a sham treatment arm. This procedure increases the risk of adverse events during treatment but has a reasonable safety profile after completion of the bronchoscopies. The overall quality of evidence regarding this procedure is moderate. For clinical practice, it would be advisable to collect data from patients systematically in independent clinical registries. Further research should provide better understanding of the mechanisms of action of bronchial thermoplasty, as well as its effect in different asthma phenotypes or in patients with worse lung function.