(RxWiki News) A few years ago, the FDA warned that certain drugs may raise the risk of cancer in children with juvenile arthritis. While it still seems these children are more prone to cancer, the drugs might not be to blame.
Children with juvenile rheumatoid arthritis are more likely than those without the condition to develop cancer. This increased risk of cancer is not caused by the use of TNF inhibitors (a class of anti-inflammatory drugs), as was previously thought.
"Ask your child's doctor about the risks of juvenile arthritis drugs."
"Since the introduction of TNF inhibitors in clinical practice, there has been concern about an increased risk of malignancy associated with them," says lead researcher Timothy Beukelman, M.D., M.S.C.E., of the University of Alabama at Birmingham.
With these concerns in mind, the FDA issued a warning in 2009 about the potential link between TNF inhibitors and the risk of cancer.
According to Dr. Beukelman, the FDA warning was based on studies that compared cancer rates between children who took TNF inhibitors and children from the general population.
"Those analyses did not account for exposure to arthritis drugs other than TNF inhibitors, such as methotrexate, or for possible carcinogenic effects of the [juvenile rheumatoid arthritis] itself," explains Dr. Beukelman.
In other words, those studies did not consider that other arthritis drugs could be increasing the risk of cancer. Nor did they consider that juvenile arthritis itself may play a role in the development of cancer.
Juvenile rheumatoid arthritis is the most common form of arthritis in children. Like its adult counterpart, juvenile rheumatoid arthritis is a disease in which inflammation causes pain and swelling around the joints.
A substance in the body called tumor necrosis factor (TNF) is thought to play a role in many inflammatory diseases, including arthritis. TNF inhibitors are drugs made to reduce inflammation by blocking the inflammatory process itself.
For their study, Dr. Beukelman and colleagues identified 7,812 children with juvenile rheumatoid arthritis. Of these children, 1,484 were treated with TNF inhibitors.
The researchers compared cancer rates between these arthritis patients and children with other chronic diseases like asthma and ADHD.
The children with juvenile rheumatoid arthritis were about three to four times more likely to develop cancer, compared to those with a different chronic illness.
Despite the small sample size, the researchers were intrigued to find that no cancer developed in any of the arthritis patients treated with TNF inhibitors.
Dr. Beukelman concludes that there is a clear increased risk of cancer in children with juvenile rheumatoid arthritis. However, he believes that TNF inhibitors are not responsible for all of this increased risk.
"At least part of the increased risk, and perhaps even all of it, appears to be attributable to the disease itself, or to other medications use in treatment such as methotrexate," Dr. Beukelman explains.
"TNF inhibitors may possibly be associated with an increased risk of cancer; our study did not have enough patients to definitively answer this question,” he says. "But based on our findings, the amount of risk that the TNF inhibitors may be responsible for appears to be much smaller than initially suspected."
This study was funded by the National Institutes of Health, the Agency for Healthcare Research and Quality, and the Food and Drug Administration. The results are published in the journal Arthritis & Rheumatism.