Incidence of and predictive factors for lung cancer in patients with rheumatoid arthritis: A retrospective long-term follow-up study.

Objective: To determine the incidence and predictive factors of lung cancer in rheumatoid arthritis (RA).

Methods: We conducted a retrospective follow-up study of patients who were diagnosed with RA at our institution between April 2001 and December 2022. Pulmonary complications were evaluated using high-resolution computed tomography at RA diagnosis. Patients were followed until the diagnosis of lung cancer, diagnosis of other malignancies, death, loss to follow-up, or the end of the study.

Results: Among 771 RA patients, 3.5% were diagnosed with combined pulmonary fibrosis and emphysema (CPFE), 4.9% with interstitial lung disease (ILD) alone, and 6.0% with emphysema alone. During follow-up (mean of 9.3 years), the crude incidence rates of lung cancer per 1,000 patient-years were 2.9 in all patients, 47.8 in CPFE patients, 10.5 in ILD patients, 11.9 in emphysema patients, and 0.8 in patients without these complications. The standardized incidence ratios (95% confidence intervals [CI]) compared with the general population were 2.53 (1.29-3.77) for male patients and 0.89 (0.57-1.16) for female patients. In Fine-Gray regression analysis, adjusted hazard ratios (95% CI) of lung cancer were 13.48 (3.14-57.85) for CPFE, 6.42 (1.42-29.09) for ILD alone, and 4.65 (1.18-18.30) for emphysema alone versus without these complications, and 1.02 (1.01-1.04) per additional 1 pack-year for smoking history. These factors were not associated with the risk of other malignancies.

Conclusion: Close monitoring of lung cancer is needed for RA patients with smoking history and pulmonary complications, especially CPFE.