Bronchial thermoplasty (BT) can now “confidently” be offered to patients with severe asthma and a baseline FEV₁ 30-50%, Australian researchers say.

The most severely obstructed patients have sometimes been excluded from thermoplasty because of safety concerns about transient worsening of asthma symptoms, according to Associate Professor David Langton of the Department of Thoracic Medicine, Frankston Hospital, Victoria.

But a prospective study of 68 patients from the Australian BT Registry has found no difference in outcomes between those with FEV₁ <50% and those with FEV₁ ≥50% despite concerns that the potential for worsening of symptoms post-procedure would preferentially impact those with the least functional reserve.

The procedures were conducted at three major teaching hospitals in Victoria, NSW and Queensland.

Using the minimal clinically significant change in Asthma Control Questionnaire score (ACQ) of 0.5, the study found 86.7% of all participants were responders to BT.

In the patients who were taking maintenance oral corticosteroids at baseline, BT led to a significant reduction in the daily dose (from 12 mg to 4.8 mg) and half the patients were weaned off oral steroids completely.

The study found improvements in ACQ, the weaning of oral corticosteroids, exacerbation frequency and the reduction in reliever medication requirement were similar in both groups irrespective of baseline FEV_1.

Adverse events were also similar in both groups.

“We further subdivided the Group 1 patients into two subgroups, namely 1a: FEV₁ <40% predicted, n=16, and 1b: FEV₁ 40-<50% predicted, n=16,” the study said.

“In Group 1a, there were 4 adverse events per 48 procedures, or 8.3%, and that value was still less than the 12.0% adverse event rate in Group 2 where the FEV₁ was ≥50% predicted.”

“The adverse event rate in Group 1b was 2 per 48 procedures or 4.1%, and the difference between Groups 1a and 1b was not statistically significant (p=0.3).”

The authors, including Professor Francis Thien and others, said the study was the first comprehensive clinical evaluation of BT in patients with an FEV₁ less than 50% predicted.

“It paves the way for a change in practice in those jurisdictions that do not currently endorse BT in these more severely obstructed patients.”

“In the original randomized trials of BT, the floor limitation in FEV₁% predicted to participation was chosen arbitrarily, on the basis of maintaining patient safety, given the novelty of the intervention at that time.”

“However, with the passage of time, these restrictions have been potentiated, with the result that deserving patients may have been denied a beneficial treatment.”

“This study demonstrates that BT can confidently be offered to asthmatic patients with an FEV₁ 30-50% predicted without risk of more frequent or more severe adverse events, and with the expectation of the same degree of response as patients with better lung function.”