SALT LAKE CITY, Oct. 24 -- Asthma symptoms can be controlled by using heat to destroy smooth muscle tissue in the large airways, a researcher reported here.
The experimental technique, dubbed bronchial thermoplasty, is also safe and well-tolerated, although the treatment caused transient worsening of asthma symptoms, according to Michel Laviolette, M.D., of Laval University in Québec City, Quebec.
The technique uses a bronchoscopic catheter with an expandable, computer-controlled heating element on the end. The catheter is inserted into airways greater than three mm in diameter that branch off the mainstem bronchi, with the exception of the right middle lobe, Dr. Laviolette said at CHEST 2006, the meeting of the American College of Chest Physicians.
Action Points
- Advise patients who ask that smooth muscle constriction in the airways plays a central role in asthma and note that this study suggests that destroying the muscle with a bronchoscopic technique will safely alleviate symptoms.
- Caution that the technique is not yet approved.
- This study was published as an abstract and presented orally at a conference. These data and conclusions should be considered to be preliminary as they have not yet been reviewed and published in a peer-reviewed publication.
In the study, patients underwent three 30-minute treatments, during which the heating elements were activated about 45 times. Control patients had three office visits, but no treatment.
The theory behind the approach is that the symptoms of asthma are caused by a combination of smooth muscle contraction and inflammation, Dr. Laviolette said. If the smooth muscle is destroyed by controlled heating, part of the problem will be solved, he added.
To test the efficacy and safety of the idea, Dr. Laviolette and colleagues at Laval and nine other centers randomized 109 patients with moderate-to-severe asthma to get either the thermal treatment or standard medical management, but the trial was not blinded.
A new trial, now accruing patients, will use a sham bronchoscopy to maintain blinding, Dr. Laviolette said.
The volunteers in the current study were all taking inhaled corticosteroids and long-acting beta-2 agonists. For volunteers to be eligible, withdrawal of the beta-2 agonists had to cause the asthma to worsen, he said.
The researchers found that patients in the thermoplasty arm had 407 adverse events (mainly shortness of breath, cough, and wheezing) compared with 106 such events among control patients.
But most of those adverse events took place during the treatment phase, Dr. Laviolette said, and resolved within a few days. During the 12-month follow-up period, respiratory adverse events were similar between the arms.
During follow-up and at the end of the study, there was no difference between the arms in terms of the one-second forced expiratory volume (FEV1) nor in bronchial hyper-responsiveness, he said.
On the other hand, a range of other measures showed statistically significant improvements, including mild exacerbation rates, number of symptom-free days, use of rescue medication, and quality of life, Dr. Laviolette said.
The main outcome measure was the number of mild exacerbations, he said, and analysis showed that the thermoplasty resulted in a 50% reduction from baseline, compared to controls. The difference was statistically significant at P=0.018.
The benefits appear to be real, commented Paul Selecky, M.D., of Hoag Memorial Presbyterian Hospital in Newport Beach, Calif., who moderated the session in which Dr. Laviolette presented his data.
But because only the larger airways are treated, "the question is why and what is the mechanism," Dr. Selecky said.
His co-moderator, Roberto Benzo, M.D., of the University of Pittsburgh, said that while the improvements are statistically significant, "they have a way to go yet" before the technique is acceptable to physicians.
The study was financed by Asthmatx, Inc., of Mountain View, Calif., which makes the catheter and other equipment used in the trial. The technique is not approved for any therapeutic use.
Primary Source
Chest
Source Reference: Laviolette M et al. "Reduction In Mild Exacerbation Rates And Improvement In Asthma Status Following Bronchial Thermoplasty." Chest 2006; 130(4): 109S-a.