Rheumatoid arthritis (RA) is a common joint disease that results in severe joint pain and deformity. This disease is related to the immune system that protects the body from infections. Some of the drugs used for severe RA act against the immune system of the body. There has been a suspicion among physicians that these drugs may increase the risk of developing cancers of the blood and lymph system, including lymphoma.

A large study in Quebec, Canada evaluated the risk of blood cancers (leukemias) and lymphoma among nearly 24,000 individuals with RA who receive drugs against the immune system. They found that the risk of developing lymphomas very definitely increased and the risk was mainly with the use of the cyclophosphamide - a drug used both for RA and many cancers. The use of cyclophosphamide approximately doubled the risk of getting lymphomas.

Though not many individuals with RA develop lymphomas, and cyclophosphamide is often of great benefit in this disease, it is a risk worth keeping in mind when treating rheumatoid arthritis.