OP0001 Risk of malignancy in children with juvenile idiopathic arthritis: a register-based cohort study
Authors: B. Delcoigne, A. Horne, J. Askling
Journal: Annals of the Rheumatic Diseases (2018)

<h3>Background</h3> The risk of malignancies, in particular malignant lymphomas, in Juvenile Idiopathic Arthritis (JIA) patients is low but has been reported to be elevated compared to the general population. <h3>Objectives</h3> To assess the risk of cancer in patients with JIA in comparison to non-JIA individuals. <h3>Methods</h3> Register-based cohort study of patients with a first JIA diagnosis recorded from 1987 to 2015, based on data retrieved from the Swedish Patient Register (with information on hospitalizations (1987 and onwards) and outpatients visits (2001 and onwards)), and the Swedish Cancer Register (compiling data on all invasive cancers in Sweden (since 1958)). JIA patients were matched (on sex and age) to five non-JIA individuals sampled from the Swedish child population. All participants were followed up from six months after date of 2nd visit with a JIA diagnosis (for JIA patients) or the corresponding date (for non-JIA individuals) until the first date of the following events: cancer diagnosis, migration, death, 18 years of age, or 31 December 2015. The occurrence of malignancies was compared through standardised incidence rates (SIR). The same analysis was rerun allowing participants to be followed up through adult ages (age at 31 December 2015). <h3>Results</h3> 7461 JIA patients and 36 747 non-JIA individuals were identified and followed up, with a median follow up time of 4.7 years. Twelve malignancies (among which 6 lymphomas) were recorded among the JIA patients and 40 (7 lymphomas) among the non-JIA individuals, giving a rate for all cancers of 30/100000 person-years and 20/100000 person-years respectively, and a rate ratio of 1.48 (95% Confidence Interval (CI): 0.78 to 2.82). When defining the outcome as a malignant lymphoma, the rates for JIA and non-JIA were 15 and 3.5/100000 person-years, respectively, and the rate ratio was 4.2 (95% CI: 1.4 to 12.5). Allowing the follow-up to cover ages above 18 did not substantially alter these two rate ratios. When restricting the study period to new-onset JIA diagnosed from July 2005 to December 2015, the rate for all cancers were 19.8/100000 person-years (JIA) and 21.1/100000 person-years (non-JIA), providing a rate ratio of 0.94 (95% CI: 0.27 to 3.22) when the age at the end of follow-up was 18 years. The rate ratio was 1.60 (95% CI: 0.68 to 3.74) when the follow-up covered all ages until end of 2015 (maximum 29 years of age). There were too few outcome cases to further restrict to malignant lymphomas. <h3>Conclusions</h3> JIA patients are at increased risk to develop malignant lymphoma. The low numbers of cancer cases in JIA patients underscores that the absolute risk is low, but hampered modelling inferences on the association between cancer and DMARDs in this cohort of JIA patients followed from disease onset. <h3>Disclosure of Interest</h3> B. Delcoigne: None declared, A. Horne: None declared, J. Askling Grant/research support from: Johan Askling has or has had research agreements with Abbvie, BMS, MSD, Pfizer, Roche, Astra-Zeneca, Eli Lilly, Samsung Bioepis, and UCB, mainly in the context of safety monitoring of biologics via ARTIS. Karolinska Institutet has received remuneration for JA participating in advisory boards arranged by Pfizer and Eli Lilly.