J.F. Simard1, M. Neovius1, S. Hagelberg2, J. Askling1. 1Clinical Epidemiology Unit, Karolinska Institutet; 2Pediatric Rheumatology Unit, Astrid Lindgren Children's Hospital, Karolinska University Hospital, Stockholm, Sweden

Background: Adverse events reports suggest an elevated rate of malignancy in juvenile idiopathic arthritis (JIA) treated with biologic therapies, leading to a recent black box warning for these drugs. The interpretation of these signals is hampered by the scarcity of data on the underlying malignancy risks in JIA in the absence of biologics therapy.
Objectives: To assess the occurrence and risk of cancer in JIA compared to the general population.
Methods: Through linkage with the national Swedish Patient Register (inpatient discharges 1969-2007, and specialized outpatients visits 2001-2007), we identified a national JIA cohort (n=9,055). For each patient, five general-population comparators were identified (n=45,275). Through linkages to the Swedish Cancer, Census, and Death Registers, and registers of drug use, occurrence of cancer, vital status through 2007, and start of a biologic therapy was determined. History of malignancy at start of follow-up led to exclusion from the study. Relative risks of first primary cancer in biologics-naïve patients were estimated using Poisson regression, a priori stratified by year of earliest JIA identification(Results: In the biologics-naïve JIA cohort, 63 malignancies were observed during 131,039 person-years compared to 274 cancers during 662,659 person-years in the population comparator (0.5 vs. 0.4 cases/1000 person-years, RR=1.2, 95%CI 0.9-1.6). Patients with JIA first identified before 1987 were not at increased cancer risk, whereas patients identified 1987 or later were significantly associated with incident lymphoproliferative cancers (RR=3.8, 95%CI 1.4-9.9, 7 cancers in JIA vs 10 in comparator) and cancers overall (RR=2.6, 95%CI 1.3-5.1, 12 JIA cancers vs 26). Sensitivity analyses did not reveal any ready explanation for this heterogeneity.
Conclusion: Though absolute risks are low, we found an elevated risk of malignancy among biologics-naïve patients with JIA identified during the recent 20 years. This may have implications for the interpretation of cancer signals in patients with JIA treated with newer therapies.
Disclosure of Interest: J. Simard: None Declared, M. Neovius: None Declared, S. Hagelberg Consultant for: Abbott Scandinavia, J. Askling Grant/Research Support from: Included are scientific analyses using data from the Swedish Biologics Register ARTIS that is run by the Swedish Society for Rheumatology. For the maintenance of this register, the Swedish Society for Rheumatology has received funding, independent of the conduct of these scientific analyses, from Schering-Plough, BMS, Wyeth, Abbott Laboratories, and Roche, Speakers Bureau: financial disclosures of < 2000 USD in speaker's honorarium for presentations of results from safety studies based on data from the Swedish Biologics Register at scientific meetings which in turn had received funding or were organized by sponsors of this meta-analysis.

Citation: Ann Rheum Dis 2010;69(Suppl3):81

Session: Abstract Session: Epidemiology and outcomes


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