Bronchial thermoplasty in severe asthma: food for thoughts

Asthma is a complex inflammatory disorder of the airways characterized by airway hyper-responsiveness and variable, reversible, airflow obstruction. Bronchial thermoplasty (BT) is a new modality for treating asthma. It targets airway smooth muscles (ASM) by delivering a controlled specific amount of thermal energy (radiofrequency ablation) to the airway wall through a dedicated catheter. The use of bronchial thermoplasty has been widely discussed for its potential in the treatment of asthma, since it seems to be able to reduce the symptoms of asthma. The definitive study for BT (AIR2 trial) employed a randomized, double-blind, sham-controlled design and enrolled 288 subjects with severe persistent asthma from 30 US and international centers. The results of the AIR2 trial demonstrated clinically significant benefits of BT compared with the sham group at one year post-treatment, including an improvement in asthma-related quality of life, 32% reduction in severe exacerbations, 84% reduction in emergency department visits for asthma symptoms, and a 66% reduction in time lost from work/school/other daily activities because of asthma symptoms. Preclinical work showed that ASM is reduced after BT by at least 3 years after treatment. The recent article from the ARI2 trial study group analyses the long-term safety and effectiveness of BT in patients with severe persistent asthma and demonstrates the 5-year durability of the benefits of BT in the control of symptoms and safety. It supports the evidence that reduction in asthma attacks, ER visits, and hospitalizations for respiratory symptoms are maintained for at least 5 years. There is a pressing need to understand the underlying mechanism(s) of BT and how the delivered heat is translated into clinical benefit. This necessitates additional investigation to identify disease and patient characteristics that would enable accurate phenotyping of positive responders to avoid unnecessary procedures and risks.