Persistence of lung hyperinflation and small airway dysfunction in school-aged children with cystic fibrosis treated with elexacaftor-tezacaftor-ivacaftor: results from the real-world MODUL-CF study

Background Trapped gas (TG) and ventilation inhomogeneity (VI) are early markers of altered small airway function (SAF) in cystic fibrosis (CF) lung disease. The evolution of these markers in children with CF (chCF) treated with elexacaftor-tezacaftor-ivacaftor (ETI) remains poorly understood. Using data from multiple breath washout (MBW) and body plethysmography (pleth) from a national, real-world cohort of school-aged chCF, we tested the hypothesis that VI and TG do not consistently return to normal levels following ETI therapy. Methods Data from MBW and pleth tests were collected from seven centers prior to ETI initiation (Month, M0), after a year of treatment (M12), and at M6 (when available). Analyses were conducted to assess the evolution of percent predicted (pp) residual volume (ppRV), total lung capacity (ppTLC), and the ppRV/TLC ratio, as well as the difference between pp functional residual capacity (ppFRC) pleth and ppFRC MBW as markers of TG. Global and regional VI indices were compared to those of age- and gender-matched healthy controls. Results A total of 192 chCF aged from 6 to 18 years at ETI initiation underwent MBW at M0 and M12. Significant reductions were observed in ppRV, ppTLC, ppRV/TLC, and TG. However, 28% of the chCF cohort had ppRV/TLC values >120% at M12. MBW-derived outcomes improved significantly, but 51.9% of the cohort had LCI 2.5 values at M12 that had not returned to healthy control levels. Conclusion ETI significantly improved SAF. However, not all outcome measures returned to normal, indicating residual lung disease in some chCF.