Study Eases Arthritis Drug Cancer Fears

Patients Taking TNF Inhibitors Had No Increase in Cancer Risk Over 6 Years

By Salynn Boyles
WebMD Health News

Reviewed By Louise Chang, MD

Oct. 29, 2009 -- Rheumatoid arthritis patients who take the biologic drugs Remicade, Humira, and Enbrel do not appear to have an increased risk for developing cancer in the first few years of use, researchers in Sweden report.

The study is one of the largest and longest population-based investigations ever into the cancer-causing potential of the drugs, known as tumor necrosis factor (TNF) inhibitors.

TNF inhibitors were introduced a decade ago, and they represent a significant advance in the treatment of patients with rheumatoid arthritis, Crohn's disease, and other diseases of the immune system who do not respond to traditional treatments.

Concerns that the drugs may cause cancer emerged soon after they were introduced, and the research examining the question has been mixed.

The new findings should reassure patients, but questions remain about the short-term and long-term safety of TNF-blocking drugs, rheumatologist Eric Matteson, MD, of Mayo Clinic in Rochester, Minn., tells WebMD.

The Swedish researchers found no difference in cancer risk among rheumatoid arthritis patients who did and did not take the drugs over six years of follow-up.

"We have to remain vigilant about the possibility that these drugs are associated with an increased risk for cancer, and make sure we use the drugs appropriately," he says. "They should only be used in the patients who really require them."

TNF Blockers Safe?

Also known as TNF blockers, TNF inhibitors target the TNF-alpha protein that is linked to inflammation and is overproduced in inflammatory diseases like rheumatoid arthritis.

TNF-alpha is also a key player in helping the body fight cancer, leading investigators to speculate that blocking it may promote cancer growth.

In the newly published study, researchers from Stockholm's Karolinska University Hospital analyzed data from several Swedish health registries.

The analysis compared cancer incidence among patients who took either Remicade, Humira, or Enbrel with patients who didn't.

It included 6,366 patients who started the TNF-blocking drugs between 1999 and 2006 and roughly 70,000 patients who were either not treated or took other types of drugs.

The researchers found little difference in cancer incidence among patients who did and did not take the TNF inhibitors. Patients who took the TNF-blocking drugs for the full six years of the study had the same cancer risk as patients who took no drugs at all for their rheumatoid arthritis.

There was a suggestion of an increase in cancer risk in patients taking the biologic drugs in the first year of use, but not in the years that followed.

"Our research indicates the overall cancer risk is the same for rheumatoid arthritis patients on (immune-system suppressing) therapies and those not taking medications for the disease," lead researcher Johan Askling, MD, and colleagues write, adding that "given several remaining uncertainties, continued vigilance remains prudent."

TNF Blockers and Skin Cancer

Two recent studies raised new fears that TNF-blocking drugs increase the risk for nonmelanoma skin cancers.

In one, researchers reported that patients taking TNF inhibitors had a 34% increased risk for nonmelanoma skin cancers, compared with patients taking other disease-modifying antirheumatic drugs (DMARDs).

In another, the TNF-blocking drugs appeared to increase the risk for developing nonmelanoma cancers by about 70%, compared to treatment with a traditional DMARD.

Both were presented at the annual meeting of the American College of Rheumatology in mid-October, where experts warned patients on the drugs to check their bodies regularly for abnormal growths that can signal skin cancer.

Given concerns about the potential risk for both infection and cancer in patients who take TNF-blocking drugs, Matteson says it is important that prescribing physicians use them only in patients who have few other options.

He tells WebMD "the jury is still out" on whether they are being over prescribed.

"The majority of patients with rheumatoid arthritis do just as well with non-biologic treatments," he says.

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SOURCES: Askling, J. Arthritis & Rheumatism, November 2009; vol 60: pp 3180-3189.

Eric Matteson, MD, rheumatologist, professor of medicine, Mayo Clinic, Rochester, Minn.

News release, Wiley-Blackwell.

FDA: "Q&A - TNF Blockers."

WebMD Medical Reference: "Biologics for Rheumatoid Arthritis Treatment."

WebMD Health News: "Medications for RA Linked to Skin Cancer."

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