Interstitial Lung Abnormalities and Lung Cancer Risk in the National Lung Screening Trial

Background: Some interstitial lung diseases are associated with lung cancer. However, it is unclear whether asymptomatic interstitial lung abnormalities convey an independent risk. Objectives: The goal of this study was to assess whether interstitial lung abnormalities are associated with an increased risk of lung cancer. Methods: Data from all participants in the National Lung Cancer Trial were analyzed, except for subjects with preexisting interstitial lung disease or prevalent lung cancers. The primary analysis included those who underwent low-dose CT imaging; those undergoing chest radiography were included in a confirmatory analysis. Participants with evidence of reticular/reticulonodular opacities, honeycombing, fibrosis, or scarring were classified as having interstitial lung abnormalities. Lung cancer incidence and mortality in participants with and without interstitial lung abnormalities were compared by using Poisson and Cox regression, respectively. Results: Of the 25,041 participants undergoing low-dose CT imaging included in the primary analysis, 20.2% had interstitial lung abnormalities. Participants with interstitial lung abnormalities had a higher incidence of lung cancer (incidence rate ratio, 1.61; 95% CI, 1.30-1.99). Interstitial lung abnormalities were associated with higher lung cancer incidence on adjusted analyses (incidence rate ratio, 1.33; 95% CI, 1.07-1.65). Lung cancer-specific mortality was also greater in participants with interstitial lung abnormalities. Similar findings were obtained in the analysis of participants undergoing chest radiography. Conclusions: Asymptomatic interstitial lung abnormalities are an independent risk factor for lung cancer that can be incorporated into risk score models.