Effect of smoking cessation on CT imaging in patients with Chronic Obstructive Pulmonary Disease: A systematic review

BackgroundSmoking cessation is the only intervention known to affect disease progression in patients with COPD as measured by the rate of change in forced expiratory volume/1s (FEV1) over time. The need for new drugs to modify the progression of COPD is well recognised. We hypothesised that changes on CT in relation to smoking cessation may relate to changes in response to disease-modifying drugs, and therefore as a novel quantitative biomarker of drug efficacy. CT biomarkers of emphysema and airway wall thickness are increasingly used in research, but there has not been a systematic appraisal of the evidence to assess how these biomarkers evolve with a change in smoking exposure in COPD patients. MethodsWe searched MEDLINE, Embase, the Cochrane Library (Cochrane Database of Systematic Reviews, Cochrane Central Register of Controlled Trials (CENTRAL)), and Web of Science to 10th September 2019. We included longitudinal studies of smoking COPD patients who had CT scans before and after smoking cessation. Two review authors (DC, SA) independently screened studies, extracted outcome data and assessed the risk of bias, with a third reviewer (JRH) arbitrating conflicts. ResultsFour studies were included in the final analysis. Three studies measured CT markers of lung density, which all, perhaps counter-intuitively, showed a significant decrease with smoking cessation. One study measured CT markers of airway wall thickness, which also significantly decreased with smoking cessation. Authors conclusionsSmoking cessation in COPD patients causes a fall in lung density, but the magnitude of the effect has not been rigorously assessed. One study has reported a decrease in airway wall thickness with smoking cessation. The number of studies is small, with some risk of bias. This question remains important for COPD researchers and requires further studies, in particular to assess whether changes with smoking cessation may model changes in response to novel pharmaceutical agents, and how to handle change in smoking status in relation to longitudinal observational imaging studies in COPD.