Swedish researchers conducted a study to determine whether the increased risk of malignant lymphomas in patients with rheumatoid arthritis (RA) was the result of environmental and genetic factors rather than a consequence of the disease itself. For their study, the researchers looked at 76,527 patients hospitalized with RA between 1964 and 1999. The participants were followed for >3 decades, and any occurrences of cancer were reported. In addition, to rule out genetic factors, the scientists looked at the incidence of malignant lymphomas in the first-degree relatives of the patients.
The results showed a significant increase in the risk of malignant lymphomas in RA patients.
The investigators concluded that lymphomas complicating RA appear to be a direct consequence of the inflammation or its treatment. There was no increase in the risk of cancer among first-degree relatives with RA.