Juvenile Idiopathic Athritis Associated with Increased Cancer Risks
The study “found a 4-fold increased rate of malignancy compared to general population rates,” reported Beth L. Nordstrom, PhD, MPH, United BioSource Corporation, Lexington, Massachusetts, and colleagues.
Cancer risk was elevated primarily among patients administered methotrexate (28% of those with JIA). That could implicate methotrexate as a risk factor for cancer, or might indicate that more severe JIA symptoms, which are more likely to be treated with methotrexate, are associated with an elevated cancer risk. Adult rheumatoid arthritis patients taking methotrexate also face elevated lymphoma risk.
Importantly, both JIA and methotrexate might be factors in cancer risk. “(B)iologics-naïve JIA was associated with more than double the risk of cancer compared to matched controls,” the authors reported.
The authors analyzed data for 3,605 children diagnosed with JIA and 37,689 non-JIA patients using the PharMetrics Patient-Centric Database, which contains medical and pharmaceutical claims for more than 60 million privately-insured US patients from more than 95 US health insurance plans. Overall incidence rates for diagnosed malignancies, other than nonmelanoma skin cancer and carcinoma in situ, were 66.95 cases per 100,000 person-years (95% CI, 1-3-132.5) among patients previously diagnosed with JIA, compared to 23.2 per 100,000 person-years (95% CI, 12.2-34.2) for non-JIA patients. The incidence rate for patients with JIA was also significantly higher than rates for the general US population, calculated with data from the US Surveillance, Epidemiology, and End Results (SEER) database (Standardized Incidence Ratio [SIR]=4.03, 95% CI, 2.56-5.99).
There were too few cases of each specific type of cancer to allow multiple subset analyses, but the SIR for JIA was significantly elevated for lymphoma in particular, when JIA cohort rates were compared to SEER rates (SIR=14.81;95% CI, 7.62-25.67).
The authors emphasized findings among biologics-naïve patients with JIA; the study was “among the first to our knowledge to examine malignancy risk in biologics-naïve JIA patients from a natural history of disease standpoint rather than looking for cancer as a potential adverse event associated with the treatment of JIA,” they wrote.
The study was funded by Wyeth/Pfizer, which employs several of the study's coauthors. Dr. Nordstrom's employer was contracted by Wyeth/Pfizer to conduct this study.