Bronchial Thermoplasty: Innovative Drug-Free Treatment of Bronchoconstriction in Asthma

In 2011, nearly 8% of the population presents symptoms of asthma, including frequent episodes of breathlessness, wheezing and cough. Over the past 15 years, our understanding of this chronic disease has improved to the point that most patients can control their symptoms with appropriate medication. However, more than 7% of the patients suffer from severe refractory asthma, defined by poorly controlled symptoms even with high-dose combinations of inhaled corticosteroid (anti-inflammatory) and long-acting bronchodilator (LABA).

Severe refractory asthma is poorly controlled
by the current options LABA-corticosteroid inhalers

Shortness of breadth and wheezing are caused by the contraction of muscles lining the airways in response to allergens, exercise or cold air. But what is responsible for this uncontrollable bronchoconstriction? With age, the airway walls of asthmatics become gradually thicker due to a phenomenon known as “airway remodeling”, fostered by chronic airway inflammation. Inflammatory cells inhabiting the airways release mediators that induce a gradual increase in thickness of the muscle layer, decrease their capacity to relax during inspiration, and raise their sensitivity to triggers by amplifying neural control. The severity of asthma attacks is proportional to the thickness of the airway muscle layer. While most treatments include corticosteroids to suppress the inflammation, they fail to reduce airway wall thickness.

Bronchoconstriction is caused by an abnormally thick
layer of smooth muscles in the airway walls

In 2010, the FDA approved an innovative therapy for severe refractory asthma: the Alair® Bronchial Thermoplasty System (Asthmatx Inc.). This drug-free approach involves the delivery of radiofrequency energy to the large airways by inserting a flexible bronchoscope through the nose or the mouth. While this thermal energy damages the airway smooth muscles and the surface layers of epithelial cells, only the epithelia regenerate, thus leaving a thinner layer of muscles after each session. This treatment requires three sessions of one hour, during which the smooth muscle layer is restored to normal thickness.

A thinner layer of smooth muscles reduces the ability of the airways
to contract, narrow and spasm during an asthma attack

Several clinical trials, namely “The Asthma Intervention Research” (AIR) trial, “The Research in Severe Asthma” (RISA) trial, and “The Asthma Intervention Research 2” (AIR2) trial, demonstrated that the adverse effects were reasonable given the significant benefits to patients with severe refractory asthma, which translated into reduced symptoms of asthma, less hospitalization, and better quality-of-life (Asthma Quality of Life Questionnaire) over a period of at least 36 months. Nonetheless, all patients must be monitored during up to six weeks after the onset of treatment because exacerbations may occur while the protective epithelial barrier is regenerating.

Whereas drugs provide temporary relief of bronchoconstriction,
bronchial thermoplasty is a long lasting therapy

It is important to note that bronchial thermoplasty may not eliminate the need for medication. Since the chronic inflammation continuously promotes airway wall thickening, a combination of corticosteroids and low doses of LABA may allow these patients to gain back control over the disease. Also, long-term follow-ups will indicate at which frequency thermoplasty should be conducted to maintain full benefits. Whereas the long-term side-effects of the procedure have not been reported yet, thermoplasty has been used successfully for the treatment of lung cancer over the past decade, with positive outcomes lasting more than five years. Eventually, thermoplasty may become common practice for most asthmatic patients for long-term prevention or reduced severity of asthma attacks, while decreasing medication.   

Qualified physicians may contact Asthmatx to receive training for this new treatment of severe refractory asthma. In the US, physicians in 20 states already use The Alair® Bronchial Thermoplasty System.

Click here for more information on Dr. Maryse Picher, Ph.D