Coexistent malignant conditions in rheumatoid arthritis – A population-based cross-sectional study

Objectives: The aim of this study was to evaluate if association exist between rheumatoid arthritis and malignant diseases. Methods: A cross-sectional study was conducted comparing rheumatoid arthritis patients with age and gender matched controls regarding the proportion of patients with comorbid malignant conditions. Chi-square tests and t-tests were used for univariate analysis. A logistic regression model was used for multivariate analysis. The study was performed utilising the medical database of Clalit Health Services. Results: The study group included 11 782 rheumatoid arthritis patients and 57 973 controls. The total proportion of malignancies was significantly higher in the study group than in the control group (21.4% vs 11.2%; P<.001). The disease for which there was the strongest association among patients with rheumatoid arthritis was non-Hodgkin's lymphoma (1.1% vs 0.6%; P<.01). After multivariate analysis, lung cancer was not found to be significantly associated with rheumatoid arthritis. Conclusion: Rheumatoid arthritis is associated with several malignant disorders, in particular non-Hodgkin's lymphoma. Appropriate measures for non-Hodgkin's lymphoma screening in this patient population should be considered.