Airway smooth muscle mass reduction after Bronchial Thermoplasty; the TASMA randomized controlled trial

Background: Bronchial Thermoplasty (BT) is a bronchoscopic treatment for severe asthma during which airways are treated with radio-frequent energy and that aims to improve asthma control by reducing airway smooth muscle (ASM). Aim: Determine the effect of BT on ASM mass before and after BT and to compare this with the non-treated right middle lobe (RML) and delayed BT control group. Methods: After obtaining airway biopsies, 11 severe asthma patients were randomized to either direct BT or to 6 months delayed BT treatment (in this control group re-biopsies after 6 months of standard care were obtained). Airway biopsies were taken 6 months post-BT in all patients. ASM mass (% of total biopsy area) was measured by automatic digital image analysis on 2 desmin-stained sections per biopsy. Results: 6 months after BT mean (SD) ASM mass significantly decreased from 11.25 (4.8)% to 4.8 (2.2) % for pre-and post-BT respectively (p=0.007) (n=11, 44 sections). In the non-BT-treated RML, 6 months after BT, ASM mass was 7.3 (±6.2) % vs 10.3 (4.9) % pre BT (p=0.13) (n=9, 36 sections). In the control group, after 6 months of standard care, ASM mass was 10 (±6.1) % vs 7.15 (±4.3) % at the first measurement (p=0.63) (n=4, 16 sections). Conclusions: ASM mass significantly decreased 6 months following BT treatment. No significant change in ASM mass was found in controls or the untreated RML.