A controversial topic in juvenile idiopathic arthritis: Association between biologic agents and malignancy

Over the last 2 decades, the usage of biological agents in the treatment of juvenile idiopathic arthritis (JIA) has been a successful and promising approach in controlling disease activity and preventing chronic sequelae. However, there are ongoing concerns about the long-term safety data and side-effect profile. We aimed to present preliminary data on the incidence of malignancy in patients with JIA treated with biological agents versus the general population rates in Turkey.

A single-center hospital-based cohort study was performed to analyze cancer occurrence among JIA patients treated with biologic agents during the observation period between January 2004 and May 2019. As reference data for direct standardization, age, gender, and calendar year-specific incidence rates from the Turkish cancer registry were used. The standardized incidence ratio (SIR, ratio of cancers observed to expected) was generated with 95% confidence intervals.

The study sample consisted of 1023 JIA patients who had been treated with biologic or non-biologic agents. In the biologic-experienced group (n = 656), the mean age (at the study) was 16.7 ± 5.6 years. The mean length of follow-up was 9.9 ± 5.0 years. One cancer was detected within the observation period (SIR: 1.3, 95% CI: 0.06-6.3). The patient was an 18-year-old male who had previously received etanercept and tocilizumab until the diagnosis of the hematologic malignancy (SIR: 2.5, 95% CI: 0.1-12.6).

Patients treated with biologic agents appeared to have an increased rate of incident hematologic malignancy versus the general population in Turkey. However, before mentioning a clear causal relationship, other potential contributing factors should be taken into consideration.