Rethinking Blood Eosinophils for Assessing ICS Response in COPD: A Post-Hoc Analysis from FLAME.

Background The varied treatment response to inhaled corticosteroids (ICS) in COPD, and the increased risk of pneumonia necessitate a personalised ICS therapeutic approach. This is informed by blood eosinophil count (BEC), which predicts ICS treatment response. However, BEC appears to change in response to ICS treatment. Research question Does BEC measured on or off ICS treatment or the change in BEC during ICS treatment, best predict treatment response to ICS in COPD? Study design and methods FLAME, a 52-week, double-blind RCT compared LABA/LAMA versus LABA/ICS. Corticosteroids were prohibited during a 4-week run-in period. We chose patients previously on ICS, thereby allowing pre- and post-run-in period BEC to represent BEC on and off ICS, respectively. In this post-hoc analysis, we revisited outcome data, exploring how the three BEC biomarkers interacted with treatment response to the ICS containing regimen. Results Our study confirms that LABA/LAMA combination is superior, or at least non-inferior, to LABA/ICS in curbing exacerbations for most FLAME participants. However, higher BEC off and BEC on ICS and significant BEC suppression during ICS treatment corresponded to superior response to LABA/ICS in terms of exacerbation rate, time-to-first exacerbation, and time-to-first pneumonia. In a subgroup, including 9% of participants, BEC changed significantly during ICS treatment (≥200 cells/μL), and higher BEC on ICS did not predict ICS treatment response. For these patients, BEC off ICS and BEC change proved more predictive. Excess pneumonia risk associated with ICS appeared to be confined to patients who do not benefit from this treatment. BEC were not predictive of treatment effects on lung function and health status. Interpretation This exploratory analysis advocates preferentially using BEC off ICS or BEC change during ICS treatment for guiding ICS treatment decisions. BEC measured on ICS is less predictive of treatment response. Clinical trial registration NCT01782326