Cumulative Incidences of Lung Cancer in Various Interstitial Lung Diseases

Background Interstitial lung disease (ILD) patients often develop lung cancer. However, previous studies on the incidences of lung cancer in ILD patients focused on specific aetiologies, such as idiopathic pulmonary fibrosis (IPF). The lung cancer incidences in these patients have not been investigated, and thus, we aimed to evaluate them here. Methods ILD patients at our hospital were retrospectively reviewed. The cumulative incidences of lung cancer in patients with various ILDs were estimated with Kaplan-Meier curves and compared between ILD groups using log-rank tests. The association between several variables at initial diagnosis and lung cancer development was assessed with Cox proportional hazards regression analysis to identify predictors. Results In all, 606 ILD patients, including 161 with IPF, 133 with non-IPF idiopathic interstitial pneumonias, 160 with chronic hypersensitivity pneumonitis, 87 with connective tissue disease-related ILDs, 19 with pulmonary sarcoidosis, and 46 with other ILDs, were included. Twenty-eight patients developed lung cancer. The cumulative incidences of lung cancer at 1, 3, and 5 years were: 1.9, 5.7, and 12.3% with IPF, respectively; 0.8, 0.8, and 4.0% in non-IPF idiopathic interstitial pneumonias; 2.0, 4.6, and 11.0% in chronic hypersensitivity pneumonitis; and 1.1, 1.1, and 2.9% in connective tissue disease-related ILDs. IPF patients had a higher incidence of lung cancer than non-IPF idiopathic interstitial pneumonia patients (p = 0.036). A radiological usual interstitial pneumonia pattern, forced vital capacity value, and pack-years were associated with lung cancer development (hazard ratios 2.959, 1.031, 1.011; 95% confidence intervals 1.257–6.963, 1.006–1.057, 1.002–1.020, p = 0.013, 0.017, 0.020, respectively). Conclusions The lung cancer incidence is higher in IPF patients than in non-IPF idiopathic interstitial pneumonia patients and is equally high in patients with chronic hypersensitivity pneumonitis and IPF.