Rheumatoid Arthritis and Risk of Lung Cancer: A Nationwide Cohort Study

Introduction: There has been an increasing interest in the risk of lung cancer related to rheumatoid arthritis (RA). We investigated the association between RA and the risk of lung cancer with consideration of key confounding factors, including RA serostatus and smoking status. Methods: Using a nationwide database, we identified 51,899 patients with newly diagnosed RA between 2010 and 2017, which were matched by sex and age at a 1:5 ratio with 259,495 non -RA population. The association of lung cancer and RA was investigated using Cox regression analyses. Stratified analyses by smoking status, sex, age, and comorbidity of interstitial lung disease were conducted using the same Cox modeling. Results: During 4.5 years of follow-up, the adjusted hazard ratio of lung cancer in the patients with RA was 1.49 (95% confidence interval: 1.34-1.66). Compared with the patients with seronegative RA, an increased risk of lung cancer was not considerable in the patients with seropositive RA. In the stratified analyses, the increased risk of lung cancer was more prominent in current or previous heavy smokers with RA (interaction p value of 0.046) and male patients (interaction p < 0.001), whereas there was no substantial effect associated with age or interstitial lung disease status. Conclusions: Patients with RA had an increased risk of lung cancer compared with the non -RA group, and the risk did not differ by RA serostatus. There is a need for increased awareness of smoking cessation and potentially for regular lung cancer screening with proper risk stratification in patients with RA.