Malignancy and rheumatoid arthritis.

The occurrence of cancer is not an infrequent event in patients with rheumatoid arthritis (RA). Indeed, following diagnosis of RA at a typical age (55 years), one in five patients will be diagnosed with cancer. In the vast majority of such cases, the cancer has nothing to do with RA or its treatment; rather, it represents the "background" risk applicable to all humans. In some cases, the cancer occurs as a result of factors also associated with the risk of developing RA (eg, smoking), even though no direct link exists between the cancer and the RA. In a fraction of cases, however, the cancer is causally associated with the RA disease or its treatments. This review summarizes our current understanding of the occurrence of cancer in RA, possible links to RA disease and to traditional and newer RA treatments.