A new study indicates that certain biologic drugs do not increase cancer risk in children with juvenile idiopathic arthritis, or JIA – countering a warning last year from the U.S. Food and Drug Administration.

Although children with JIA are two to three times more likely to develop cancer than children who don’t have JIA, tumor necrosis factor-alpha blockers, also known as TNF inhibitors or anti-TNF drugs, do not appear to be the cause, according to a study presented last week at the American College of Rheumatology Annual Scientific Meeting in Atlanta. TNF inhibitors used to treat juvenile arthritis include adalimumab, or Humira, and etanercept, or Enbrel.  

“Data collected by the FDA suggested that children who receive TNF inhibitors are at an increased risk of developing malignancy compared to healthy children who do not receive TNF inhibitors. Our study shows that at least a portion of this increased risk of malignancy is likely due to JIA itself, as opposed to the TNF inhibitor alone,” explains the study’s lead investigator, Timothy Beukelman, MD, an assistant professor of pediatrics at the University of Alabama at Birmingham.

An estimated 300,000 children in the U.S. have juvenile arthritis. For this study, Dr. Beukelman used Medicaid claims to identify 7,321 American children with JIA. Of those, 3,194 were being treated with methotrexate, 1,413 were on TNF inhibitors and the rest weren’t taking either type of drug.

They found that out of 100,000 children, 59 with JIA got cancer in the space of a year compared with 23 to 27 per 100,000 in children without the condition. There were no cases of cancer in children on TNF inhibitors.

“I think that is significant given the sample size. If there were a big increase in risk [from anti-TNFs], you should have seen it in a group that large,” says Diane Brown, MD, PhD, a pediatric rheumatologist at Children’s Hospital Los Angeles and faculty member at the University of Southern California Keck School of Medicine in Los Angeles.

“This finding should not be shocking, as similar results have been demonstrated for adults with rheumatoid arthritis, especially with regard to an increased risk of lymphoma in this population,” Dr. Beukelman adds. “Our findings should mitigate some of the concerns regarding the use of TNF inhibitors for the treatment of JIA.”

If anti-TNF drugs don’t cause the increased cancer risk – what does? Dr. Beukelman’s study didn’t address that question, but, he says, “A reasonable hypothesis would be that chronic inflammation is responsible for the increased rate of malignancy. If this hypothesis is correct, then better control of JIA may help attenuate this risk.”

Dr. Brown hopes this study will help her and others in her field persuade parents that the value of trying TNF inhibitors outweighs the risk.

“I hope that parents recognize the risk of these drugs is not that bad, and treating the disease with effective medicines may cut down on inflammation and may actually decrease the risk of cancer, for all we know,” she says.

“This study is reaffirming what most rheumatologists and pediatric rheumatologists think – that the primary culprit isn’t the drug but probably is the disease,” Dr. Brown says. “Our experience with these medications is, we aren’t seeing a lot of malignancies in our patients.”