Lung cancer in connective tissue disease-associated interstitial lung disease: clinical features and impact on outcomes.

Backgrounds: Lung cancer (LC) adversely impacts survival in patients with idiopathic pulmonary fibrosis. However, little is known about LC in patients with connective tissue disease-associated interstitial lung disease (CTD-ILD). The aim of this study was to evaluate the prevalence of and risk factors for LC in CTD-ILD, and the clinical characteristics and survival of CTD-ILD patients with LC.

Methods: We conducted a single-center, retrospective review of patients with CTD-ILD from 2003 to 2016. Patients with pathologically diagnosed LC were identified. The prevalence, risk factors, and clinical features of LC and the impact of LC on CTD-ILD patient outcomes were observed.

Results: Of 266 patients with CTD-ILD, 24 (9.0%) had LC. CTD-ILD with LC was more likely in patients who were older, male, and smokers; had rheumatoid arthritis, a usual interstitial pneumonia pattern, emphysema on chest computed tomography scan, and lower diffusing capacity of the lung carbon monoxide (DLco)% predicted; and were not receiving immunosuppressive therapy. Multivariate analysis indicated that the presence of emphysema [odds ratio (OR), 8.473; 95% confidence interval (CI), 2.241-32.033] and nonuse of immunosuppressive therapy (OR, 8.111; 95% CI, 2.457-26.775) were independent risk factors for LC. CTD-ILD patients with LC had significantly worse survival than patients without LC (10-year survival rate: 28.5% vs. 81.8%, P<0.001).

Conclusions: LC is associated with the presence of emphysema and nonuse of immunosuppressive therapy, and contributes to increased mortality in patients with CTD-ILD.