Link between use of anti-TNF therapy and malignant melanoma in RA patients

According to research presented this week at the American College of Rheumatology Annual Scientific Meeting in Chicago, people taking anti-tumor necrosis factor therapies to treat rheumatoid arthritis have a higher risk of developing malignant melanoma.

Rheumatoid arthritis is a chronic disease that causes pain, stiffness, swelling, and limitation in the motion and function of multiple joints. Though joints are the principal body parts affected by RA, inflammation can develop in other organs as well. An estimated 1.3 million Americans have RA, and the disease typically affects women twice as often as men.

Anti-TNF therapies suppress the immune system and taking these medications can increase the risk of developing infections. Additionally, recent research has reported a possible connection between the use of anti-TNF therapy and certain skin cancers including malignant melanoma. Researchers from Sweden recently reviewed data to investigate the risk of malignant melanoma in patients with RA compared to the general population, and to investigate whether anti-TNF treatment such as adalimumab (Humira®), etanercept (Enbrel®) and infliximab (Remicade®) elevates malignant melanoma risk in rheumatoid arthritis.

"Anti-TNF therapies are excellent drugs that have a major impact on the health and well-being of patients with rheumatoid arthritis," says investigator, Julia Fridman Simard, ScD; assistant professor at the Clinical Epidemiology Unit, Department of Medicine at the Karolinska Institutet. "Many patients are treated with these therapies, not just in rheumatoid arthritis, and it is important to understand the potential side effects to inform treatment decisions and clinical practice."

Using information from the Swedish Biologics Register, ARTIS, linked to other national Swedish registers, the researchers identified 56,336 individuals with rheumatoid arthritis − of which 8,453 were noted as starting anti-TNF therapy, as well as reference subjects from the general population. The risks of getting a malignant melanoma or any other cancer were compared between RA patients and the general population, and between RA patients treated, and not treated, with anti-TNF therapies.

During the study, researchers recorded 32 cases of malignant melanoma among the 8,453 patients with rheumatoid arthritis taking anti-TNF therapies, and 135 cases in the 47,883 patients not taking these therapies. Compared to the general population subjects, individuals with RA were not at increased risk of malignant melanoma. Within the group of patients with RA, the risk of malignant melanoma was approximately 80 percent higher among those patients receiving anti-TNF therapy compared to those patients not receiving these drugs. Malignant melanomas accounted for around seven percent of all incident cancers among the patients with RA. In contrast to the elevated risk of malignant melanomas among patients with RA treated with anti-TNF therapy, there was no increase in the risk for all other types of cancers combined in this group.

Dr. Simard further comments, "Although these findings shed some light on the safety of anti-TNF therapy and its role in the development of malignant melanomas, it should be kept in mind that malignant melanomas accounted for only seven percent of all cancers in our population, that the overall burden of cancers in patients treated with anti-TNF therapy does not seem to be elevated, and that the absolute risk of an individual patient to develop a malignant melanoma is small. The 'number needed to treat' with anti-TNF therapy during one year for one additional malignant melanoma to occur is on the order of several thousands." She also adds, "from a clinical perspective, our findings suggest we should not forget to pay attention to skin lesions suspicious of melanomas occurring in patients treated with anti-TNF therapy, especially since the prognosis following prompt removal of early melanomas is excellent. Furthermore, more studies to identify patients at high risk are needed to help inform clinical decision making."