Elevated Cancer Risk in Patients With Juvenile Idiopathic Arthritis: Presented at EULAR

By Shazia Qureshi

AMSTERDAM, the Netherlands -- June 14, 2018 -- Children with juvenile idiopathic arthritis (JIA) appear to have an elevated risk of cancer, especially malignant lymphoma, researchers reported here at the Annual European Congress of Rheumatology hosted by the European League Against Rheumatism (EULAR).

The absolute risk of cancer was found to be low at 30 per 100,000 person-years, but this was still about 50% higher than in children without JIA.

“The underlying reasons for this increased risk are unclear,” said Anna Carin Horne, MD, Karolinska University Hospital, Stockholm, Sweden.

The researchers evaluated hospitalisation and outpatient data from the Swedish Patient Register and invasive cancer data for patients in the Swedish Cancer Register.

They found a total of 7,461 patients with a new-onset JIA diagnosis in the period from 1987 to 2015. Each of these patients was then age- and sex-matched to 5 individuals without JIA (in total 36,747).

After a median of 4.7 years of follow-up, the study found 12 malignancies, including 6 lymphomas, in the patients with JIA. Among the group of individuals without JIA, 40 malignancies, 7 of which were lymphomas, had been recorded in the registries.

The standardised incidence rate for malignant lymphoma was calculated to be 15 per 100,000 person-years for patients with JIA and 3.5 per 100,000 person-years for those without JIA (rate ratio [RR] = of 4.2; 95% confidence interval [CI], 1.4-12.5).

Looking at all cancers, the RR was 1.48 (95% CI, 0.78-2.82), which was lower than the value of 4.2 calculated for lymphomas, but still showed an elevated risk for the JIA cohort compared with the group without JIA.

However, when the researchers looked at only the final 10 years of their study period in the registry, there appeared to be no difference in all-cancer risk between the 2 groups, while for malignant lymphomas there were not enough outcome cases to analyse.

For patients who were diagnosed with new-onset JIA from July 2005 to December 2015, the incidence rate (per 100,000 person-years) for all cancers was 19.8, compared with 21.1 for the matched non-JIA controls. This meant a RR of 0.94 (95% CI, 0.27-3.22) when the children were followed up to a maximum age of 18 years, but higher at 1.60 (95% CI, 0.68-3.74) when using a longer follow-up to a maximum age of 29 years.

“The low numbers of cancer cases in JIA patients underscores that the absolute risk is low, but [it] hampered modelling inferences on the association between cancer and disease-modifying anti-rheumatic drugs in this cohort of JIA patients [who were] followed from disease onset,” said Dr. Horne. “There is no signal that the risk of cancer in JIA patients has been increasing over the last years.”

[Presentation title: Risk of Malignancy in Children With Juvenile Idiopathic Arthritis: a Register-Based Cohort Study. Abstract OP0001]

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