Effects of cyclophosphamide on the prognosis of Japanese patients with renal vasculitis associated with anti-neutrophil cytoplasmic antibody-positive microscopic polyangiitis

Background: The aim of this study was to determine the efficacy of cyclophosphamide (CY) on anti-neutrophil cytoplasmic antibody (ANCA)-positive microscopic polyangiitis (MPA) with renal involvement in Japanese patients. Methods: Eighty-two patients with newly diagnosed ANCA-positive MPA were enrolled in this retrospective study. Patients were divided into two groups based on whether they received combination therapy with a corticosteroid (CS) plus CY (CY group) or CS alone or with other therapies (non-CY group). The primary outcome was defined as the combination of death and end-stage renal disease (ESRD). Results: The CY and non-CY groups included 29 and 53 patients, respectively. In the non-CY group, 31 patients were treated with CS alone, and 22 with a combination of CS and other therapeutics. The percentage of males and mean Birmingham vasculitis activity scores were higher in the CY group than those in the non-CY group, but other factors such as age, serum creatinine, serum albumin, or CRP at baseline were equivalent in the two groups. No differences were observed in remission rates using induction therapy for the two groups. However, the survival rate 5 years after induction therapy was lower in the CY group than in the non-CY group (0.50 vs. 0.73; P = 0.041), although the hazard ratio of CY for the primary outcome adjusted for all confounding factors was 1.321 [95 % confidence interval (CI), 0.662–2.637; P = 0.171]. Conclusions: CY may not have an additive effect on induction therapy with CS for Japanese patients with renal vasculitis associated with ANCA-positive MPA.