Effect of time to start of biologic therapy on treatment response in childhood arthritis: Results from the UCAN CAN‐DU study

Objective To estimate the effect of time from symptom onset to start of biologic treatment on achieving inactive arthritis within six months in a cohort of juvenile idiopathic arthritis (JIA) patients. Methods The international UCAN CAN‐DU study prospectively enrolls JIA patients across Canada and the Netherlands. A nested cohort study was performed and biologic‐naive, non‐systemic JIA patients were included at the start of biologic therapy. The primary outcome was inactive arthritis at six months. Demographics, disease‐related parameters and treatment response were compared using (non)parametric tests between early (time symptom onset to biologic start: 0‐6 months), intermediate (7‐12 months) and late (13‐24 months) treatment groups. A logistic regression model analysed the effect of time to biologic start on the response at six months, adjusting for active joint count and physician global assessment. A graphical representation of the model was created. Results 130 children with JIA were included (early: n=35, intermediate: n =46, late; n=49), 66% were female and the median age at symptom onset was 11.0. The proportion of patients that reach inactive arthritis in the early starters (83%) was significantly higher than in late starters (57%). For each month of delay to the start of biologic treatment, the adjusted odds of having active arthritis after six months of therapy was 1.09 (Interquartile range: 1.02‐1.17, p=0.009). Conclusions Early start of biologic therapies in JIA patients was associated with a higher proportion of patients reaching inactive arthritis within 6 months, suggesting a window of opportunity to control disease activity.