Critical review of bronchial thermoplasty: where should it fit into asthma therapy?

Safety and efficacy of bronchial thermoplasty in refractory asthma with severe obstructive respiratory dysfunction

BACKGROUND

Bronchial thermoplasty (BT) is a recently developed non-pharmacological therapy for refractory bronchial asthma. Although increasing evidence has suggested that BT is effective for various phenotypes of severe asthma, its safety and efficacy in patients with severe irreversible impaired lung function are unclear.

OBJECTIVES

To assess the efficacy and safety of BT in patients with refractory asthma, including patients with a severely impaired forced expiratory volume in 1 second (FEV1).

DESIGN

This was a single-center, retrospective, observational cohort study.

METHODS

We retrospectively reviewed the medical records of 15 patients with refractory asthma (Global Initiative for Asthma step 4 or 5), including patients with severely impaired airflow limitation (% predicted pre-bronchodilator FEV1 <60%), who had undergone BT between June 2016 and January 2022. We analyzed the efficacy (change in asthma symptoms, exacerbation rate, pulmonary function, asthma medication, and serum inflammatory chemokine/cytokines before and after BT) and complications in all patients. We compared these data between patients with severe obstructive lung dysfunction [group 1(G1)] and patients with FEV1 ⩾ 60% [group 2 (G2)].

RESULTS

Six patients were in G1 and nine were in G2. Clinical characteristics, T2 inflammation, and concurrent treatment were equivalent in both groups. BT significantly improved asthma-related symptoms (measured using the Asthma Control Test and Asthma Quality of Life Questionnaire scores) in both groups. FEV1 was significantly improved in G1 but not in G2. Four patients in G2, but none in G1, experienced asthma exacerbation requiring additional systemic corticosteroids (including two requiring prolonged hospitalization) after BT. Long-term responders (patients who reduced systemic or inhaled corticosteroid without newly adding biologics in a follow-up > 2 years) of BT were identified in G1 and G2 (n = 2, 33.3% and n = 4, 44.4%, respectively).

CONCLUSION

BT in patients with refractory asthma and severe airflow limitation is equally safe and efficacious as that in patients with moderate airflow limitation.

Quantitative CT detects changes in airway dimensions and air-trapping after bronchial thermoplasty for severe asthma

OBJECTIVES

Bronchial thermoplasty (BT) can be considered in the treatment of severe asthma to reduce airway smooth muscle mass and bronchoconstriction. We hypothesized that BT may thus have long-term effects on airway dimensions and air-trapping detectable by quantitative computed tomography (QCT).

METHODS

Paired in- and expiratory CT and inspiratory CT were acquired in 17 patients with severe asthma before and up to two years after bronchial thermoplasty and in 11 additional conservatively treated patients with serve asthma, respectively. A fully automatic software calculated the airways metrics for wall thickness (WT), wall percentage (WP), lumen area (LA) and total diameter (TD). Furthermore, lung air-trapping was quantified by determining the quotient of mean lung attenuation in expiration vs. inspiration (E/I MLA) and relative volume change in the Hounsfield interval -950 to -856 in expiration to inspiration (RVC_856-950) in a generation- and lobe-based approach, respectively.

RESULTS

BT reduced WT for the combined analysis of the 2nd-7th airway generation significantly by 0.06 mm (p = 0.026) and WP by 2.05% (p < 0.001), whereas LA and TD did not change significantly (p = 0.147, p = 0.706). No significant changes were found in the control group. Furthermore, E/I MLA and RVC_856-950 decreased significantly after BT by 12.65% and 1.77% (p < 0.001), respectively.

CONCLUSION

BT significantly reduced airway narrowing and air-trapping in patients with severe asthma. This can be interpreted as direct therapeutic effects caused by a reduction in airway-smooth muscle mass and changes in innervation. A reduction in air-trapping indicates an influence on more peripheral airways not directly treated by the BT procedure.

Bronchial thermoplasty in severe asthma in Australia

BACKGROUND

Bronchial thermoplasty (BT) is an approved bronchoscopic intervention for the treatment of severe asthma. However, limited published experience exists outside of clinical trials regarding patient selection and outcomes achieved.

AIMS

To evaluate the effectiveness and safety of BT in patients with severe asthma encountered in clinical practice.

METHODS

This is a retrospective analysis of the first 'real world' data from Australia. The following outcomes were measured prior to, and 6 months following BT: spirometry, Asthma Control Questionnaire-5 (ACQ-5) score, reliever and preventer medication use and exacerbation history.

RESULTS

Twenty patients were treated from June 2014 to December 2015 at three university teaching hospitals. All subjects met the European Respiratory Society/American Thoracic Society definition of severe asthma. Mean pre-bronchodilator forced expiratory volume in 1 s was 62.8 ± 16.6% predicted (range: 33-95%). All patients were being treated with high dose inhaled corticosteroids, long-acting beta₂ agonists and long-acting muscarinic antagonists. Ten patients (50%) were taking maintenance oral prednisolone. Most subjects also required at least one of montelukast (65%), omalizumab (30%) and methotrexate (20%). ACQ-5 improved from 3.6 ± 1.1 at baseline to 1.6 ± 1.2 at 6 months, P < 0.001. Short-acting reliever use decreased from a median of 8.0-0.25 puffs/day, P < 0.001, and exacerbations requiring corticosteroids also significantly reduced. Five of 10 patients completely discontinued maintenance oral corticosteroids. Ten patients with a baseline forced expiratory volume in 1 s of <60% predicted significantly improved from 49.2 ± 9.6% to 61.8 ± 17.6%, P < 0.05. Only two procedures required hospitalisation beyond the planned overnight admission.

CONCLUSION

BT is a safe procedure which can achieve clinical improvement in those with uncontrolled symptoms and severe airflow obstruction.

Bronchial thermoplasty as a treatment for severe asthma: controversies, progress and uncertainties

INTRODUCTION

Bronchial thermoplasty is a licensed non-pharmacological treatment for severe asthma. Area covered: This article considers evidence for the efficacy and safety of bronchial thermoplasty from clinical trials and observational studies in clinical practice. Its place in the management of severe asthma, predictors of response and mechanisms of action are reviewed. Expert commentary: Bronchial thermoplasty improves quality of life and reduces exacerbations in moderate to severe asthma. Morbidity from asthma is increased during treatment. Overall, patients treated in clinical practice have worse baseline characteristics and comparable clinical outcomes to trial data. Follow-up studies provide reassurance on long-term safety. Despite some progress, future research needs to investigate uncertainties about predictors of response, mechanism of action and place in management of asthma.

Chinese consensus statement on standard procedure and perioperative management of bronchial thermoplasty

Bronchial thermoplasty (BT) is a non-pharmacologic therapy for severe asthma. The proper procedure and perioperative management are very important for the effectiveness and safety of BT. China Asthma Alliance assembled a group of experts in asthma and BT to review the literature, drew on their own experiences, discussed, and then finalized by consensus to establish this standard practice guideline. This practice guideline is designed to guide clinicians as to proper patients' selection, preoperative assessment, postoperative management and follow-up. This practice guideline also proposed "China Alair System Registry Study (NCT02206269)" as the real-world study to enhance clinical utility of BT.

Airway Inflammation after Bronchial Thermoplasty for Severe Asthma

RATIONALE

Bronchial thermoplasty is an alternative treatment for patients with severe, uncontrolled asthma in which the airway smooth muscle is eliminated using radioablation. Although this emerging therapy shows promising outcomes, little is known about its effects on airway inflammation.

OBJECTIVES

We examined the presence of bronchoalveolar lavage cytokines and expression of smooth muscle actin in patients with severe asthma before and in the weeks after bronchial thermoplasty.

METHODS

Endobronchial biopsies and bronchoalveolar lavage samples from 11 patients with severe asthma were collected from the right lower lobe before and 3 and 6 weeks after initial bronchial thermoplasty. Samples were analyzed for cell proportions and cytokine concentrations in bronchoalveolar lavage and for the presence of α-SMA in endobronchial biopsies.

MEASUREMENTS AND MAIN RESULTS

α-SMA expression was decreased in endobronchial biopsies of 7 of 11 subjects by Week 6. In bronchoalveolar lavage fluid, both transforming growth factor-β1 and regulated upon activation, normal T-cell expressed and secreted (RANTES)/CCL5 were substantially decreased 3 and 6 weeks post bronchial thermoplasty in all patients. The cytokine tumor-necrosis-factor-related apoptosis-inducing ligand (TRAIL), which induces apoptosis in several cell types, was increased in concentration both 3 and 6 weeks post bronchial thermoplasty.

CONCLUSIONS

Clinical improvement and reduction in α-SMA after bronchial thermoplasty in severe, uncontrolled asthma is associated with substantial changes in key mediators of inflammation. These data confirm the substantial elimination of airway smooth muscle post thermoplasty in the human asthmatic airway and represent the first characterization of significant changes in airway inflammation in the first weeks after thermoplasty.

Asthma

Asthma is the most common inflammatory disease of the lungs. The prevalence of asthma is increasing in many parts of the world that have adopted aspects of the Western lifestyle, and the disease poses a substantial global health and economic burden. Asthma involves both the large-conducting and the small-conducting airways, and is characterized by a combination of inflammation and structural remodelling that might begin in utero. Disease progression occurs in the context of a developmental background in which the postnatal acquisition of asthma is strongly linked with allergic sensitization. Most asthma cases follow a variable course, involving viral-induced wheezing and allergen sensitization, that is associated with various underlying mechanisms (or endotypes) that can differ between individuals. Each set of endotypes, in turn, produces specific asthma characteristics that evolve across the lifecourse of the patient. Strong genetic and environmental drivers of asthma interconnect through novel epigenetic mechanisms that operate prenatally and throughout childhood. Asthma can spontaneously remit or begin de novo in adulthood, and the factors that lead to the emergence and regression of asthma, irrespective of age, are poorly understood. Nonetheless, there is mounting evidence that supports a primary role for structural changes in the airways with asthma acquisition, on which altered innate immune mechanisms and microbiota interactions are superimposed. On the basis of the identification of new causative pathways, the subphenotyping of asthma across the lifecourse of patients is paving the way for more-personalized and precise pathway-specific approaches for the prevention and treatment of asthma, creating the real possibility of total prevention and cure for this chronic inflammatory disease.