Weighing pain relief and cancer risk: A new study may ease some fears about TNF inhibitors

During the past decade, a new class of drugs, called TNF inhibitors, has improved the lives of tens of thousands of people who suffer from painful autoimmune diseases including rheumatoid arthritis, psoriatic arthritis, and Crohn's disease. But there is a catch: the same drugs that offer unmatched pain relief today might trigger a serious cancer later on. Patients desperate for new drug therapies are forced to make a difficult choice.

Now (at least for the 1.3 million adults with rheumatoid arthritis) that decision might be a little less daunting—although still not risk free. A new study, slated to appear in the November issue of Arthritis & Rheumatism, is one of the largest and longest popoulation-based looks at cancer risks associated with TNF inhibitors. Swedish researchers identified and analyzed data from 6,366 patients who started TNF inhibitors between January 1999 and July 2006. Then compared the data to more than 60,000 rheumatoid arthritis patients not taking any medications and 8,000 taking older drugs with different mechanisms of action.

TNF (short for tumor necrosis factor) is a substance secreted by cells in the immune system. TNF regulates the immune system and plays a role in inflammation. TNF inhibitors (also called TNF blockers) are a class of drugs used to reduce pain by reducing inflammation. (If you've flipped through a magazine or watched TV lately, you've probably seen commercials for them sold under the brand names Remicade, HumiraTM, and Enbrel.) Originally prescribed only for severe cases of rheumatoid arthritis, the drugs are now used for a number of immune-related conditions, ranging from moderate to severe. But, from the start, TNF inhibitors raised worries about increased risk of cancer, particularly blood cancers.

But, at study's end, the researchers detected no additional increase in cancer risk among those patients taking TNF inhibitors. "Our research shows the overall cancer risk is the same for patients on immunosuppressant therapies and those not taking medications," says Johan Askling, MD, PhD, lead author from Karolinska University Hospital in Stockholm. But he adds that "given several remaining uncertainties, continued vigilance is prudent."

His cautionary tone is well deserved. Some studies do show an increased risk of cancer within the first few months of treatment with TNF inhibitors, possibly because the drugs may unleash the growth of otherwise small, undiagnosed tumors.

Then there is the matter of the additional black box warnings for the drugs issued as recently as last August by the Food and Drug Administration after the agency found a troubling link between TNF inhibitors and higher risk of lymphoma in children and adolescents. So, for parents making treatment choices for their children, the decision over whether or not to risk the TNF inhibitor is as grueling as ever. But, for adults, this latest study might ease a little bit of angst.