Risk of malignancy in children with juvenile idiopathic arthritis not treated with biologics

Abstract

Objective:

To estimate the relative risk of incident cancer diagnosis among patients with juvenile idiopathic arthritis (JIA) compared to patients without JIA.

Methods:

A cohort of biologics-naïve patients diagnosed with JIA between 1998 and 2007 and a matched cohort of comparators without JIA were assembled from the PharMetrics claims database. The primary outcome was any incident malignancy, excluding non-melanoma skin cancer and carcinoma in situ. Claims profiles of patients with any cancer-related diagnosis codes were reviewed to determine outcomes. Incidence rates and 95% confidence intervals (CIs) of cancer were calculated and compared between cohorts using Cox proportional hazards regression. Standardized incidence ratios (SIRs) for each cohort compared to the general population were calculated using reference rates from the US Surveillance, Epidemiology and End Results (SEER) Program.

Results:

The JIA and non-JIA cohorts included 3,605 and 37,689 patients, respectively, with a mean age of 11 years. Incidence rates of cancer were 67.0 (95% CI: 1.3–132.5) cases/100,000 person-years (PY) for JIA and 23.2 (95% CI: 12.2–34.2) cases/100,000 PY for non-JIA. Risk of cancer associated with biologics-naïve JIA was elevated (HR: 2.8; 95% CI: 0.9–8.3). The JIA cohort had a significantly elevated SIR of 4.0 (95% CI: 2.6–6.0); the non-JIA cohort was not significantly above SEER rates (SIR: 1.4; 95% CI: 0.6–2.6).

Conclusions:

We found a nearly 3-fold increased risk of cancer in biologics-naïve JIA patients, which, despite the small number of outcomes, approached significance. This finding suggests an elevated underlying risk of cancer in this disease population. © 2012 by the American College of Rheumatology