ATLANTA – The rate of cancer in children with juvenile idiopathic arthritis in the United States was at least twice as high as was the rate of cancer in children the same age without JIA, but no cancer cases were found among children with JIA who were exposed to TNF inhibitors, based on a review of a nationwide database.
The findings were presented at the annual meeting of the American College of Rheumatology.
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"Since the introduction of TNF inhibitors in clinical practice, there has been concern about an increased risk of malignancy associated with them," Dr. Timothy Beukelman of the University of Alabama, Birmingham, said in an interview. This concern increased in 2009, when a report from the Food and Drug Administration found a possible association between TNF inhibitors and malignancy in children, he said. The report prompted the FDA to issue a black box warning about the risk of pediatric malignancy from anti-TNF drugs, he said.
But the FDA report compared cancer rates in children receiving TNF inhibitors with children in the general population, which did not account for exposure to other drugs, such as methotrexate, or for possible carcinogenic effects of the JIA disease process itself, said Dr. Beukelman.
"We attempted to fill in some of the gaps in our knowledge regarding a possible background or baseline increased rate of malignancy for children with JIA," he said.
Dr. Beukelman and colleagues reviewed National Medicaid Administrative Claims data for 2000-2005. They identified 7,321 children with JIA and compared them with non-JIA control groups who had diagnoses of asthma or attention-deficit hyperactivity disorder (ADHD). Among the JIA patients, 3,194 were taking methotrexate and 1,413 were exposed to TNF inhibitors.
The standardized rate of any cancer in children with JIA was 59 per 100,000 person-years, compared with 27 per 100,000 person-years and 23 per 100,000 person-years in the control groups with asthma and ADHD, respectively. The standardized rate of leukemia and lymphoma was 25 per 100,000 person-years in the JIA group, compared with 9 per 100,000 person-years in both control groups.
Of note, the researchers found no cases of cancer in more the 1,400 children with JIA who had been exposed to anti-TNF therapy, said Dr. Beukelman said.
More research is needed to determine how disease activity in children with JIA impacts their risk for cancer, but the study findings suggest that the potential cancer risk associated with TNF inhibitors appears to be less than expected, he said.
Dr. Beukelman said that he had no financial conflicts to disclose. Some of his coinvestigators have received research grants and consulting fees from multiple pharmaceutical companies including Amgen, Centocor, and Roche.