Comparing Rituximab and Cyclophosphamide in Induction Therapy for Childhood-Onset ANCA-Associated Vasculitis: An ARChiVe registry-cohort study.

Objective: Granulomatosis with polyangiitis (GPA) and microscopic polyangiitis (MPA) are chronic life-threatening vasculitides requiring substantial immunotherapy. Adult trials identified rituximab (RTX) as an alternative to cyclophosphamide (CYC) for remission-induction of GPA/MPA. Disease rarity has limited feasibility of similar trials in pediatrics. We aim to evaluate the relative efficacy and toxicity of CYC and RTX for childhood GPA/MPA through registry-based comparative evaluation.

Methods: From A Registry of Childhood Vasculitis we identified GPA/MPA patients who received induction with RTX or CYC. Pediatric vasculitis activity score (PVAS) and pediatric vasculitis damage index (pVDI) evaluated disease activity and damage. Descriptive statistics summarized patient characteristics. RTX/CYC comparisons used logistic regression for primary outcomes of post-induction remission (PVAS=0) or low disease activity (PVAS<2). Hospital admission for adverse events and pVDI were compared using logistic regression and ordinal regression, respectively.

Results: Among 104 patients, 43% received RTX, 46% CYC, 11% both. Treatment groups did not significantly differ for diagnosis PVAS and onset age. There was no difference in remission between groups (63% overall; OR 1.07, 95% CI: 0.45, 2.52). Hospitalizations occurred in 22% of RTX patients versus 10% on CYC (OR 2.27, 95% CI: 0.73, 7.05). The median 12-month pVDI was one in both groups (OR 0.98, 95% CI 0.43, 2.22).

Conclusion: This is the first study comparing CYC and RTX for induction in pediatric GPA/MPA. No significant differences were shown in rates of remission, severe adverse events, or organ damage. Limitations included lack of standardized treatment regimens, retrospectivity, and lack of longitudinal adverse drug-related event data.