Rheumatoid arthritis is a disease that causes chronic inflammation of the joints, and it affects approximately 1.3 million adults in the United States, most of whom are over the age of 40. One of the most common treatments for rheumatoid arthritis is methotrexate. According to a study in the June 15 issue of Arthritis Care & Research, individuals with rheumatoid arthritis who are treated with methotrexate have an increased risk of melanoma, non-Hodgkin's lymphoma, and lung cancer.

Investigators from Australia studied 459 patients with rheumatoid arthritis who were treated with methotrexate in order to determine cancer risk. The patients were followed for an average of 9.3 years. The investigators found that, compared to the general population, these patients had 3-fold increase in melanoma (a malignant skin cancer), a 5-fold increase in non-Hodgkin's lymphoma (a blood cell cancer), and an almost 3-fold increase in lung cancer.

Although the mechanism behind this increased cancer risk is not yet known, the authors of the study suggested that these findings might support a role for regular skin cancer screening of all rheumatoid arthritis patients, especially because melanoma is easily treated if detected early.