Bronchial thermoplasty: has the promise been met?

Bronchial thermoplasty in severe asthma: a real-world study on efficacy and gene profiling

Background

Bronchial thermoplasty (BT) is an effective treatment in severe asthma. How to select patients who more likely benefit from BT is an unmet clinical need. Moreover, mechanisms of BT efficacy are still largely unknown. We sought to determine BT efficacy and to identify potential mechanisms of response.

Methods

This retrospective cohort study evaluated clinical outcomes in 27 patients with severe asthma: 13 with T2-high and 14 with T2-low endotype. Expression levels of 20 genes were compared by real-time PCR in bronchial biopsies performed at the third BT session versus baseline. Clinical response was measured based on Asthma Control Questionnaire (ACQ) score < 1.5, asthma exacerbations < 2, oral corticosteroids reduction of at least 50% at 12 months post-BT. Patients were classified as responders when they had at least 2 of 3 outcome measures.

Results

81% of patients were defined as responders. BT induced a reduction in alpha smooth muscle actin (ACTA2) and an increase in CD68, fibroblast activation protein-alpha (FAP), alpha-1 and alpha-2 type I collagen (COL1A1, COL1A2) gene expression in the majority of patients. A higher reduction in ubiquitin carboxy-terminal-hydrolase L1 (PGP9.5) mRNA correlated with a better response based on Asthma Quality of Life Questionnaire (AQLQ). Lower changes in CD68 and FAP mRNAs correlated with a better response based on ACQ. Lower levels of occludin (OCLN), CD68, connective tissue growth factor (CTGF), higher levels of secretory leukocyte protease inhibitor (SLPI) and lower changes in CD68 and CTGF mRNAs were observed in patients who had less than 2 exacerbations post-BT. Lower levels of COL1A2 at baseline were observed in patients who had ACQ < 1.5 at 12 months post-BT.

Conclusions

BT is effective irrespective of the asthma endotypes and seems associated with airway remodelling. Quantification of OCLN, CD68, CTGF, SLPI, COL1A2 mRNAs could be useful to identify patients with better results.

Trial registration: The study protocol was approved by the Local Ethics Committee (Azienda USL-IRCCS of Reggio Emilia—Comitato Etico Area Vasta Nord of Emilia Romagna; protocol number: 2019/0014076) and all the patients provided written informed consent before participating in the study.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13223-022-00680-4.

Bronchial Thermoplasty

Bronchial thermoplasty is an advanced therapy for severe asthma. It is a bronchoscopic procedure in which radiofrequency energy is applied to the airway wall, resulting in decreased airway smooth muscle burden. Human trials have shown that bronchial thermoplasty may reduce asthma exacerbations and improve quality of life in patients with severe uncontrolled asthma. It has been demonstrated to be a safe procedure, with most adverse events being early and mild. More studies are required to understand the precise effects of bronchial thermoplasty on the asthmatic airway and optimal parameters to appropriately select patients for this novel procedure.

Efficacy and safety of bronchial thermoplasty in clinical practice: a prospective, longitudinal, cohort study using evidence from the UK Severe Asthma Registry

OBJECTIVES

Use data from the UK Severe Asthma Registry (UKSAR) to assess the efficacy and safety of bronchial thermoplasty (BT) in routine UK clinical practice and to identify characteristics of 'responders'.

DESIGN

Prospective, longitudinal, cohort, multicentre registry study.

SETTING

All (11) UK centres performing BT.

PARTICIPANTS AND INTERVENTION

Patients receiving BT in the UK between 01/06/2011 and 30/09/2016 who had consented to data entry into UKSAR (n=133). Efficacy data were available for 86 patients with a BT baseline and at least one follow-up record. Safety data were available for 131 patients with at least one BT procedure record.

PRIMARY AND SECONDARY OUTCOME MEASURES

Efficacy: AQLQ, ACQ, EuroQol, HADS anxiety and HADS depression scores, FEV₁ (% predicted), rescue steroid courses, unscheduled healthcare visits (A&E/Asthma clinic/GP), hospital admissions and days lost from work/school.

SAFETY

peri-procedural events, device problems and any other safety-related findings. Responder analysis: differences in baseline characteristics of 'responders' (≥0.5 increase in AQLQ at 12 months) and 'non-responders'.

RESULTS

Following Bonferroni correction for paired comparisons, mean improvement in AQLQ at 12 months follow-up compared with BT baseline was statistically and clinically significant (0.75, n=28, p=0.0003). Median reduction in hospital admissions/year after 24 months follow-up was also significant (-1.0, n=26, p<0.0001). No deterioration in FEV₁ was observed. From 28 patients with AQLQ data at BTBL and 12-month follow-up, there was some evidence that lower age may predict AQLQ improvement. 18.9% (70/370) of procedures and 44.5% (57/128) of patients were affected by an adverse event; only a minority were considered serious.

CONCLUSIONS

Improvement in AQLQ is consistent with similar findings from clinical trials. Other efficacy outcomes demonstrated improving trends without reaching statistical significance. Missing follow-up data impacted this study but multiple imputation confirmed observed AQLQ improvement. The safety review suggested BT is being performed safely in the UK.

Procedural and short-term safety of bronchial thermoplasty in clinical practice: evidence from a national registry and Hospital Episode Statistics

OBJECTIVE

Bronchial thermoplasty (BT) is a novel treatment for severe asthma. Its mode of action and ideal target patient group remain poorly defined, though clinical trials provided some evidence on efficacy and safety. This study presents procedural and short-term safety evidence from routine UK clinical practice.

METHODS

Patient characteristics and safety outcomes (procedural complications, 30-day readmission and accident and emergency (A&E) attendance, length of stay) were assessed using two independent data sources, the British Thoracic Society UK Difficult Asthma Registry (DAR) and Hospital Episodes Statistics (HES) database. A matched cohort (with records in both) was used to estimate safety outcome event rates and compare them with clinical trials.

RESULTS

Between June 2011 and January 2015, 215 procedure records (83 patients; 68 treated in England) were available from DAR and 203 (85 patients) from HES. 152 procedures matched (59 patients; 6 centres), and of these, 11.2% reported a procedural complication, 11.8% resulted in emergency respiratory readmission, 0.7% in respiratory A&E attendance within 30 days (20.4% had at least one event) and 46.1% involved a post-procedure stay. Compared with published clinical trials which found lower hospitalisation rates, BT patients in routine clinical practice were, on average, older, had worse baseline lung function and asthma quality of life.

CONCLUSIONS

A higher proportion of patients experienced adverse events compared with clinical trials. The greater severity of disease amongst patients treated in clinical practice may explain the observed rate of post-procedural stay and readmission. Study of long-term safety and efficacy requires continuing data collection.

Bronchial thermoplasty: reappraising the evidence (or lack thereof)

Bronchial thermoplasty (BT) involves the application of radiofrequency energy to visible proximal airways to selectively ablate airway smooth muscle. BT is the first nonpharmacologic interventional therapy approved by the US Food and Drug Administration (FDA) for severe asthma. This approval was based on the results of the pivotal Asthma Intervention Research (AIR)-2 trial, which is the only randomized, double-blind, sham-controlled trial of BT. The primary end point of the AIR-2 trial was improvement in the Asthma Quality of Life Questionnaire (AQLQ). The results of the AIR-2 trial have generated enormous interest, controversy, and confusion regarding the true efficacy of BT for severe asthma. Current marketing of BT highlights its use for patients with "severe" asthma, which is interpreted by most practicing clinicians as meaning oral corticosteroid dependence, frequent exacerbations, or a significantly reduced FEV1 with a poor quality of life. Did the AIR-2 trial include patients with a low FEV1, oral steroid dependence, or frequent exacerbations? Did the trial show efficacy for any of the primary or secondary end points? The FDA approved the device based on the reduction in severe asthma exacerbations. However, were the rates of asthma exacerbations, ED visits, or hospitalizations truly different between the two groups, and was this type of analysis even justified given the original study design? This commentary is designed to specifically answer these questions and help the practicing clinician navigate the thermoplasty literature with confidence and clarity. We carefully dissect the design, conduct, and results of the AIR-2 trial and raise serious questions about the efficacy of bronchial thermoplasty.

Bronchial thermoplasty: a new treatment paradigm for severe persistent asthma

Patients with severe asthma represent only a minority of the total asthma population; however, they account for the majority of the mortality, morbidity, and health care-related cost of this chronic illness. Bronchial thermoplasty is a novel treatment modality that employs radiofrequency energy to alter the smooth muscles of the airways. This therapy represents a radical change in our treatment paradigm from daily repetitive dosing of medications to a truly long-term and potentially permanent attenuation of perhaps the most feared component of asthma--smooth muscle-induced bronchospasm. A large, multicentered, double-blinded, randomized controlled trial employed the unprecedented (but now industry standard for bronchoscopic studies) approach of using sham bronchoscopy as a control. It demonstrated that bronchial thermoplasty is safe, improved quality of life, and decreased frequency of severe exacerbations in the treatment group compared to the control group. Although the mechanism of action of bronchial thermoplasty is not currently completely understood, it should be considered as a valid and potentially valuable option for patients who have severe persistent asthma and who remain symptomatic despite inhaled corticosteroids and long-acting beta-2 agonists. Such patients should however be carefully evaluated at centers with expertise in managing severe asthma patients and with physicians who have experience with this promising new treatment modality.

Optimal management of severe/refractory asthma

Asthma is a chronic inflammatory disease of the airways, affecting approximately 300 million people worldwide. Asthma results in airway hyperresponsiveness, leading to paroxysmal symptoms of wheeze, cough, shortness of breath, and chest tightness. When these symptoms remain uncontrolled, despite treatment with high doses of inhaled and ingested corticosteroids, asthmatic patients are predisposed to greater morbidity and require more health care support. Treating patients with severe asthma can be difficult and often poses a challenge to physicians when providing ongoing management. This clinical review aims to discuss the definition, prevalence and evaluation of severe asthmatics, and provides a review of the existing pharmacologic and non-pharmacologic treatment options.

Bronchial thermoplasty in asthma

Currently available treatments for asthma provide satisfactory control of the disease in most cases. However, a significant number of patients do not respond to such treatments (i.e., do not achieve effective symptom relief). One novel approach to treating asthma is bronchial thermoplasty, in which the airway smooth muscle is specifically and directly treated. This procedure delivers radiofrequency energy to the airways in order to reduce smooth muscle-mediated bronchoconstriction. In this article, we present the thermoplasty technique, summarizing the results of the major randomized clinical trials of the procedure, as well as discussing its mechanisms of action and potential adverse effects. We also propose strategies for the future clinical use of this new treatment.

Controversies in the evaluation and management of chronic cough

Chronic cough that cannot be explained after basic evaluation is a common reason for patients to be referred to respiratory outpatient clinics. Asthma, gastroesophageal reflux, and upper airway disorders frequently coexist with chronic cough. There is some controversy as to whether these conditions are causes or aggravants of cough. Heightened cough reflex sensitivity is an important feature in most patients. There is good evidence that it is reversible when associated with upper respiratory tract infection, angiotensin-converting enzyme inhibitor medications, and chronic cough associated with eosinophilic airway inflammation. In many patients, heightened cough reflex sensitivity is persistent and their cough is unexplained. There are few therapeutic options for patients with unexplained chronic cough. There is a pressing need to understand the genetic, molecular, and physiological basis of unexplained chronic cough and to develop novel antitussive drugs that down-regulate cough reflex sensitivity.