Optimal dose of intravenous cyclophosphamide during remission induction therapy in ANCA-associated vasculitis: A retrospective cohort study of J-CANVAS

Objectives To identify the optimal dose of intravenous cyclophosphamide (IVCY) for induction therapy for anti-neutrophil cytoplasmic antibody-associated vasculitis.Methods We retrospectively assessed patients with antibody-associated vasculitis who received IVCY every 2-3 weeks during the remission induction phase. The associations of the IVCY dose with infection-free survival and relapse-free survival were analysed using a Cox regression model. We compared patients in three categories: very low-dose (VLD), low-dose (LD), and conventional dose (CD) (<7.5 mg/kg, 7.5-12.5 mg/kg, and >12.5 mg/kg, respectively). The non-linear association between IVCY dose and the outcomes was also evaluated.Results Of the 80 patients (median age 72 years), 12, 42, and 26 underwent the VLD, LD, and CD regimens, respectively, of whom 4, 3, and 7 developed infection or died. The adjusted hazard ratios for infection or death were 4.3 (95% confidence interval (CI) 0.94-19.8) for VLD and 5.1 (95% CI 1.21-21.3) for CD, compared with LD. We found the hazard ratio for infection or death increased when the initial IVCY dose exceeded 9 mg/kg. Relapse-free survival did not differ clearly.Conclusion Low-dose IVCY (7.5-12.5 mg/kg) may result in fewer infections and similar relapse rates compared with the conventional regimen (>12.5 mg/kg).