OBJECTIVE: To longitudinally evaluate effects of smoking cessation on quantitative CT in a lung cancer screening cohort of heavy smokers over 4 years. METHODS: After 4 years, low-dose chest CT was available for 314 long-term ex-smokers (ES), 404 continuous smokers (CS) and 39 recent quitters (RQ) who quitted smoking within 2 years after baseline CT. CT acquired at baseline and after 3 and 4 years was subjected to well-evaluated densitometry software, computing mean lung density (MLD) and 15th percentile of the lung density histogram (15TH). RESULTS: At baseline, active smokers showed significantly higher MLD and 15TH (-822+/-35 and -936+/-25 HU, respectively) compared to ES (-831+/-31 and -947+/-22 HU, p〈0.01-0.001). After 3 years, CS again had significantly higher MLD and 15TH (-801+/-29 and -896+/-23 HU) than ES (-808+/-27 and -906+/-20 HU, p〈0.01-0.001) but also RQ (-813+/-20 and -909+/-15 HU, p〈0.05-0.001). Quantitative CT parameters did not change significantly after 4 years. Importantly, smoking status independently predicted MLD at baseline and year 3 (p〈0.001) in multivariate analysis. CONCLUSION: On quantitative CT, lung density is higher in active smokers than ex-smokers, and sustainably decreases after smoking cessation, reflecting smoking-induced inflammation. Interpretations of quantitative CT data within clinical trials should consider smoking status. KEY POINTS: * Lung density is higher in active smokers than ex-smokers. * Lung density sustainably decreases after smoking cessation. * Impact of smoking cessation on lung density is independent of potentially confounding factors. * Smoke-induced pulmonary inflammation and particle deposition influence lung density on CT.
Type of Publication:
Journal article published