The risk of malignancy among biologic-naive pediatric psoriasis patients: A retrospective cohort study in a US claims database

Background: Little published literature exists regarding malignancy risk in pediatric psoriasis patients. Objective: To compare malignancy risk in biologic-naive pediatric psoriasis patients with a matched pediatric population without psoriasis. Methods: This retrospective cohort study used IMS LifeLink Health Plan Claims data covering 1998-2008. Cancer incidence was compared with the US Surveillance, Epidemiology, and End Results (SEER) data using standardized incidence ratios (SIR), and between cohorts using Cox models. Results: Among 9045 pediatric psoriasis patients and 77,206 comparators, 18 probable or highly probable cancers were identified. Pediatric psoriasis patients had a nonsignificantly lower incidence than comparators (hazard ratio [HR] 0.43, 95% confidence interval [CI] 0.05-3.54). The HR increased to 1.67 (95% CI 0.54-5.18) when cancer diagnosed during the first 90 days of follow-up was included. The pediatric psoriasis cohort had a significantly increased lymphoma rate compared with SEER (SIR 5.42, 95% CI 1.621-2.94), but no significant increase relative to the comparator cohort. Limitations: Misclassification of disease and outcome might have occurred with patients in the claims database. Conclusion: Patients with pediatric psoriasis showed no significant increase in overall cancer risk compared with those without psoriasis. A potential increased risk for lymphoma was observed when compared with the general population.