TNF therapy does not raise cancer risk in RA patients; overall cancer risk comparable to those not taking immunosuppressive drugs

A recent study by Swedish researchers found that rheumatoid arthritis (RA) patients did not experience an elevated cancer risk in the first 6 years after starting anti-tumor necrosis factor (TNF) therapy. The research team, led by Johan Askling, M.D., Ph.D., from Karolinska University Hospital in Stockholm, Sweden assessed the short-term and medium-term cancer risk for RA patients using anti-TNF therapies: infliximab, adalimumab, and etanercept. Details of the study appear in the November issue of Arthritis & Rheumatism, a journal of the American College of Rheumatology published by Wiley-Blackwell.

TNF is a cytokine (substance secreted by immune system cells) that regulates the body's immune system and is involved in inflammation. TNF inhibitors (or TNF blockers) are a class of therapies used to reduce inflammation in chronic inflammation such as RA. The common immunosuppressant drugs and those included in the study are Remicade®, HumiraTM, and Enbrel®. As these therapies are used to treat chronic inflammatory illnesses, the long-term inhibition of TNF raises concerns for increased risk of infections and cancer.

This study, one of the largest and longest population-based assessments of cancer risks associated with immunosuppressive therapy, included data from several Swedish databases including the Biologics Register, the Cancer Register, and the Early RA Register. Researchers identified and analyzed data from 6,366 patients who started anti-TNF therapy between January 1999 and July 2006. Data from patients using TNF inhibitors was compared with other groups of RA patients—61,160 not taking medication, 4015 using methotrexate (the gold standard in RA treatment) and 4,015 taking combinations of disease-modifying anti-rheumatic drugs (other than TNF inhibitors).

Results show there were 240 first primary cancers diagnosed during the 25,693 person-years of follow-up in the patients using anti-TNF therapy who had no history of cancer at the onset of immunosuppressant treatment. When compared to the larger national RA cohort who did not receive TNF inhibitors or have a history of cancer, the relative risk of anti-TNF therapy was 1.00 and remained unchanged for those taking immunosuppressant drugs for up to 6 years. "Our research indicates the overall cancer risk is the same for RA patients on immunosuppressant therapies and those not taking medications for the disease," confirmed Dr. Askling, but adds that "given several remaining uncertainties, continued vigilance remains prudent."

Rheumatoid Arthritis (RA) is an autoimmune disease characterized by chronic inflammation in the joints, joint tissue, and other organs and is the most common form of inflammatory arthritis. A 2004 report from the World Health Organization (WHO) estimates 23.7 million people worldwide (1.3 million U.S. adults) are afflicted with RA, with 75% of those cases found in women.