Therapies commonly used to treat rheumatoid arthritis do not seem to cause cancer, according to research presented at the American College of Rheumatology Annual Scientific Meeting in San Francisco, Calif.

TNF-antagonists have been used since 1998; overall, they have been given to more than 600,000 people worldwide. It has been unclear whether blocking tumor necrosis factor is associated with an increased risk of developing cancer in patients with RA. Some studies have shown an association between RA itself and certain types of cancer - namely lung cancer and, above all, hematological malignancies - though the reasons for this increased risk are uncertain.

Researchers in Spain recently looked to BIOBADASER, a drug registry established in 2001 for the active long-term follow up of the safety of biological therapies in rheumatology patients. As of December 2007, the registry included 4,529 patients with RA who had been treated with TNF antagonists. Information includes medical records information about the patients (e.g., gender, date of birth, diagnosis, date of diagnosis), treatment information (e.g., type, dates of initiation and discontinuation) and occurrence of adverse events.

Researchers looked at this group of patients, and a second control group of patients with RA not included in the BIOBADASER registry that were followed from 1999 to 2005, to estimate the incidence of cancer in patients with RA who were treated with TNF antagonists versus those not treated with TNF antagonists.

After a total follow up of 14,001 person years, (11,758 from the BIOBADASER group and 2,243 from the second group), researchers found 29 cases of cancer in the control group and 70 in the TNF-treated group.

After adjusting for age, sex, disease duration, and disease activity, they found that the incidence of developing cancer in the TNF group was very close to that of the non-TNF treated control group (0.92), leading them to conclude that TNF antagonist exposure does not seem to be associated with a higher risk for developing malignancy in RA patients.

"Despite foreseen fears, blocking the tumor necrosis factor does not make patients more prone to develop cancer," explains Loreto Carmona, MD, PhD; director of research unit, Fundacion Espanola de Reumatologia (Spanish Foundation of Rheumatology), Madrid, Spain. "All on the contrary, blocking the inflammation cascade may help diminish the overall risk of cancer in these patients."