One Bronchial Thermoplasty Treatment Beats Three for Asthma

May 20, 2019

A single bronchial thermoplasty procedure in which a hyperpolarized gas MRI is used to prioritize six airways in the lungs of patients with uncontrolled asthma is more effective than three standardized sessions of bronchial thermoplasty, new research shows.

"We got the end point we wanted and we also saw adverse events related to the procedure significantly reduced," said Chase Hall, MD, from the Washington University School of Medicine in St. Louis.

Although patients with severe, difficult-to-treat asthma constitute only 5% to 10% of the population with asthma, they consume a disproportionate percentage of the global asthma budget and costs of pharmacology.

"Moving forward, if this gets approved, it would mean patients would need less time off work, the procedure would cost less, and patients would have fewer complications with a similar benefit," Hall said during a late-breaking clinical trials session at the American Thoracic Society (ATS) 2019 International Conference in Dallas.

To test this new approach, the research team randomized 15 patients with uncontrolled asthma to guided bronchial thermoplasty, in which patients underwent volumetric CT and MRI with the 129Xe contrast agent (MagniXene, Xemed).

"The patients inhale a gas that goes into their lungs and we image that gas to see where it's going. That gives us an idea of where gas is not able to make it," Hall explained. Segments of the lung that received the lowest amount of gas were targeted for treatment in the guided group.

The other 15 patients — randomized to unguided bronchial thermoplasty — underwent three standard treatment sessions at 3-week intervals: one for the right lower lobe, one for the left lower lobe, and one for both upper lobes.

Median age of the study participants was 45 years, 80% were women, 63% were on chronic oral corticosteroids, 43% were on omalizumab, and FEV1% predicted was 69.7.

Guided Ventilation Procedure

Hyperpolarized Xe MRI ventilation heatmap image registered to CT scan of the chest in a patient with normal ventilation (left) and severe asthma (right). Note the heterogeneous ventilation in the patient with severe asthma.

After treatment, the mean increase in Asthma Quality of Life Questionnaire (AQLQ) score from baseline was significant in the guided group (= .006). However, after the first unguided treatment, the mean increase in AQLQ score was not significant (= .06).

At 12 weeks, after all three sessions had been completed in the unguided group, the mean increase in AQLQ scores was similar in the guided and unguided groups (0.96 vs 1.46; = .201).

"The primary end point was achieved," Hall told Medscape Medical News. One guided treatment was comparable to three unguided treatments at 12 weeks.

At 12 months, AQLQ scores and asthma control were similar in the two groups.

Improvement in Adverse Events

There were significantly fewer asthma-related adverse events in the guided group than in the unguided group (12 vs 24), and the rate of asthma exacerbations was lower (33% vs 73%; = .025).

Airway inflammation that causes an acute but transient exacerbation of asthma symptoms follows the procedure "about 60% of the time," and often these events require oral corticosteroids and hospitalization, Hall reported. However, "the adverse effects are short term. Five-year outcome data show the effect is durable."

Periprocedure events can limit the use of bronchial thermoplasty "to some degree," Hall explained, because it can be "hard to get it approved through insurance."

The insurance issue arises because guidelines recommend that bronchial thermoplasty be performed "in adults with severe asthma only in the context of an Institutional Review Board–approved independent systematic registry or a clinical study" (Eur Respir J. 2014;43:343-373). However, bronchial thermoplasty was fairly new when those guidelines were published, and no long-term data were available, he pointed out.

"Now we need to do this study in a larger patient population," Hall said.

More Research Needed

"I don't really know what the long-term effects of this one study are," said Laren Tan, MD, from Loma Linda University Health in California, "but I am very excited to see where this leads us."

"For a long time, we've been trying to figure out who would benefit most from bronchial thermoplasty," said Tan, who initiated bronchial thermoplasty at his center and has extensive experience with the procedure. "Using MRI and this gas is going to be helpful."

However, leaving some areas untouched might not be good in the long term, he cautioned.

Biopsies he and his team performed after bronchial thermoplasty showed that "there was about a 50% decrease in airway smooth muscle in the middle lobe." That is an area not directly treated by standard bronchial thermoplasty, he explained. "That shows us that even though we may not be treating in specified areas, there is a global diffusion additive effect."

The MRI component could lead to longer wait times, which might be difficult in some hospitals, but Tan said he agrees that "one treatment is better than three."

"There is a toll to being sedated three times," he said. "The recovery time between each treatment can be quite lengthy. Once is definitely helpful."

Tan presented research Sunday at the ATS meeting that showed that patients with better control of their asthma have lower levels of anxiety.

Improvements in anxiety scores were associated with the improvement in asthma that resulted from the procedure, not the procedure itself, he reported.

In the cohort of 22 patients, anxiety scores improved substantially from baseline to final treatment, and quality of life improved dramatically.

"Asthma causes anxiety. You can't breathe. It can also cause depression," Tan said. "We are hoping to bring awareness that there is a mental component to uncontrolled asthma. It's not just the lung we need to treat."

Xemed provided the hyperpolarized gas for study by Hall's team, and Boston Scientific provided catheters. Tan is a consultant for Boston Scientific.

American Thoracic Society (ATS) 2019 International Conference: Abstract P721, presented May 19, 2019; late-breaking clinical trials session, presented May 20, 2019.

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