Background The risk of cancer, including any secular trends in risk, in patients with juvenile idiopathic arthritis (JIA) is incompletely understood.
Methods We performed a register-based cohort study of patients with JIA from 2001 until 2017, identified via the Swedish Patient Register. Patients with JIA were matched to five population reference subjects. Patients and referents were followed up for incident cancers (via linkage to the Swedish Cancer Register) until 18 years of age or 31 December 2016.
Results Among the 6721 patients with JIA, we observed 10 incident malignancies (5 lymphoproliferative cancers) during 34 951 person-years of follow-up, corresponding to an excess incidence of 0.09 cancers per 1000 person-years (one extra case per 11 000 patients per year), an HR for cancer (all sites) of 1.4 (95% CI 0.7 to 2.9) and an HR for lymphoproliferative malignancies of 3.6 (95% CI 1.1 to 11.2). The rates of cancer in JIA did not increase over the study period. We noted no differences in the excess risk comparing periods before and after the introduction of biologic disease-modifying antirheumatic drugs (bDMARDs).
Discussion Children and adolescents with JIA are at a slightly increased risk of lymphoproliferative (but not of other) malignancies. At the group level, there is no sign that this risk has increased further after the introduction of bDMARDs.
- juvenile idiopathic arthritis
- DMARDs (biologic)
- outcomes research
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Contributors ACH, BD and JA made the study design. BD gathered and analysed the data. ACH drafted the manuscript, and all authors revised the paper in keeping with important content and provided final approval before publishing. All authors agreed to be accountable for the accuracy of the work.
Funding This study was supported by the Swedish Rheumatism Association.
Competing interests ACH has received speakers compensation from Sobi and Novartis. JA has or has had research agreements with AbbVie, BMS, MSD, Pfizer, Roche, AstraZeneca, Eli Lilly, Samsung Bioepis and UCB, mainly in the context of safety monitoring of biologics via ARTIS. Speakers bureau: Karolinska Hospital has received compensation for ACH from AbbVie and SOBI. The Karolinska Institute has received remuneration for JA participating in advisory boards arranged by Pfizer and Eli Lilly.
Patient and public involvement statement We have patient representatives, both in the clinic and in research. The chair of the Rheumatic Youth Organization of Sweden is our main representative and support our current study and agree that it is of greatest importance. The Rheumatic Youth Organisation and the Swedish Rheumatism Association will help distribute our results so they reach all affected patients and families physicians as well as physicians
Patient consent for publication Not required.
Ethics approval The Regional Ethical Review Board in Stockholm granted ethical approval (DNR: 2015/1844-31/2).
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement Data are available upon reasonable request.
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