Bronchial thermoplasty in asthma: current perspectives

Figures & data

Table 1 Summary of the clinical trials and long-term follow-up of BT in asthma

Study	Study design	Number of patients	Inclusion criteria	Exclusion criteria	Endpoints	Outcomes improved	Outcomes unchanged	Key findings
Safety study^Citation30	Prospective, non-randomized	16 BT	≥18 years, mild to moderate asthma, Stable symptoms for preceding 6 weeks	Respiratory infection in preceding 6 weeks, ≥2 LRTI requiring antibiotics in previous year, >4 puffs of SABA in 24 hours	Safety; not powered for efficacy outcomes; PFTs, PEF, symptom-free days, AHR, rescue medication use reported	Morning PEF (12 weeks); Evening PEF (12 weeks); Symptom-free days (12 weeks) AHR	FEV1 Rescue SABA use	No major adverse events Improved AHR and symptom-free days No structural abnormalities on CT chest
AIR trial^Citation31	Randomized controlled trial	56 control 56 BT	Age 18–65, moderate to severe persistent asthma, FEV1 60%–85% pred, Methacholine PC20 <8 mg/mL, Stable symptoms for preceding 6 weeks, Worsening asthma symptoms upon LABA withdrawal	Respiratory infection in preceding 6 weeks, ≥3 LRTI requiring antibiotics in previous year	Primary: frequency of mild exacerbations Secondary: PFTs, PEF, AHR, rescue medication use, asthma symptom scores	Frequency of mild exacerbations Morning PEF Rescue medication use ACQ score AQLQ score Symptom-free days	FEV1 AHR	Reduced mild exacerbation frequency Improved ACQ, AQLQ scores
RISA trial^Citation32	Randomized controlled trial	17 control 15 BT	Age 18–65, Severe persistent asthma, FEV1 ≥50% pred, Airway hyperresponsiveness		Primary: safety Secondary: change in OCS and ICS, rescue medication use, PEF, FEV1, methacholine PC20, asthma symptom scores	Steroid stable phase: SABA use preBD FEV1 ACQ and AQLQ scores Post-steroid wean: SABA use ACQ and AQLQ score	Steroid stable phase: OCS and ICS dosing PEF Symptom-free days PC20 Post-steroid wean: OCS and ICS dosing PEF Symptom-free days PC20 FEV1	Improved FEV1 post-BT during steroid stable phase Increased respiratory adverse events noted during the treatment period No difference in adverse events in the post-treatment period Procedure is safe in severe asthma
AIR-2 trial^Citation33	Randomized, double-blind, sham controlled trial	101 control 196 BT	Age 18–65, Severe persistent asthma, FEV1 ≥60% pred, Airway hyperresponsiveness (PC20 <8 mg/mL), AQLQ ≤6.25	Life-threatening asthma, Chronic sinus disease, Use of immunosuppressants, β-adrenergic blocking agents, or anticoagulants, ≥3 hospitalizations for asthma in previous year, ≥3 LRTI in previous year, ≥4 OCS pulses for asthma in previous year	Primary: change in AQLQ Secondary: symptom scores, symptom-free days, PEF, rescue medication use, FEV1, severe exacerbations, emergency department visits, hospitalizations, days missed from work/school	AQLQ score Severe exacerbations Days lost from school/work	PEF Symptom-free days ACQ score Rescue medication use Hospitalizations	Improved AQLQ scores 32% reduction in severe exacerbations 84% reduction in ED visits 66% reduction in days lost work/school
AIR trial 5-year follow-up^Citation34		24 control 45 BT	See AIR above	See AIR above		Improved AHR out to 3 years		No increase in respiratory events Stable FEV1 and FVC over 5 years
RISA trial 5-year follow-up^Citation35		14 BT	See RISA above	See RISA above		Persistent decrease in hospitalizations and ED visits		No increase in respiratory events Stable FEV1 and FVC over 5 years
AIR-2 trial 5-year follow-up^Citation36		162 BT	See AIR-2 above	See AIR-2 above		Sustained reduction in exacerbations and ED visits over 5 years		No increase in respiratory events Stable FEV1 and FVC over 5 years

Abbreviations: BT, bronchial thermoplasty; LRTI, lower respiratory tract infection; SABA, short-acting beta agonist; PFT, pulmonary function testing; PEF, peak expiratory flow; AHR, airway hyperresponsiveness; FEV₁, forced expiratory volume in 1 second; FVC, forced vital capacity; AIR, asthma intervention research; pred, predicted; PC₂₀, provocative concentration causing a 20% decline in FEV₁; LABA, long-acting beta agonist; ACQ, asthma control questionnaire; AQLQ, asthma quality of life questionnaire; RISA, research in severe asthma; OCS, oral corticosteroid; ICS, inhaled corticosteroid; preBD, prebronchodilator; AIR-2, asthma intervention research-2; ED, emergency department.

Figure 1 Airway histology before and after BT.

Notes: (A and C) Hematoxylin and eosin and (B and D) trichrome stain. Prominent ASM is seen in this patient with severe asthma, with significantly reduced ASM following treatment with BT. Thin arrow: airway epithelium; thick arrow: ASM.
Abbreviations: BT, bronchial thermoplasty; ASM, airway smooth muscle.

CoxGMillerJDMcWilliamsAFitzgeraldJMLamSBronchial thermoplasty for asthmaAm J Respir Crit Care Med2006173996596916456145

 PubMed Web of Science ®Google Scholar

CoxGThomsonNCRubinASAIR Trial Study GroupAsthma control during the year after bronchial thermoplastyN Engl J Med2007356131327133717392302

 PubMed Web of Science ®Google Scholar

PavordIDCoxGThomsonNCRISA Trial Study GroupSafety and efficacy of bronchial thermoplasty in symptomatic, severe asthmaAm J Respir Crit Care Med2007176121185119117901415

 PubMed Web of Science ®Google Scholar

CastroMRubinASLavioletteMAIR2 Trial Study GroupEffectiveness and safety of bronchial thermoplasty in the treatment of severe asthma: a multicenter, randomized, double-blind, sham-controlled clinical trialAm J Respir Crit Care Med2010181211612419815809

 PubMed Web of Science ®Google Scholar

ThomsonNCRubinASNivenRMAIR Trial Study GroupLong-term (5 year) safety of bronchial thermoplasty: asthma intervention research (AIR) trialBMC Pulm Med201111821314924

 PubMed Web of Science ®Google Scholar

PavordIDThomsonNCNivenRMResearch in Severe Asthma Trial Study GroupSafety of bronchial thermoplasty in patients with severe refractory asthmaAnn Allergy Asthma Immunol2013111540240724125149

 PubMed Web of Science ®Google Scholar

WechslerMELavioletteMRubinASAsthma Intervention Research 2 Trial Study GroupBronchial thermoplasty: long-term safety and effectiveness in patients with severe persistent asthmaJ Allergy Clin Immunol201313261295130223998657

 PubMed Web of Science ®Google Scholar