Treatment of polyarteritis nodosa and microscopic polyangiitis with poor prognosis factors: A prospective trial comparing glucocorticoids and six or twelve cyclophosphamide pulses in sixty‐five patients

Objective Because the optimal cyclophosphamide (CY) treatment duration for severe polyarteritis nodosa (PAN) without virus infection and microscopic polyangiitis (MPA) has not been established, we conducted a trial to compare the effectiveness of 6 versus 12 CY pulses given in combination with corticosteroids (CS). Methods Sixty‐five (18 PAN, 47 MPA) previously untreated patients were randomized to receive 12 (n = 34) or 6 (n = 31) CY pulses combined with CS. PAN and MPA were histologically proven or met ACR criteria. All patients presented ≥1 factor of severity according to the five factor score (FFS). CY pulses were administered every 2 weeks for 1 month, then every 4 weeks. The end point of the study was the number of events (relapses and/or deaths) occurring in each group, analyzed according to an intention‐to‐treat strategy. The outcome was evaluated by Cox proportional hazards analysis. Results The baseline characteristics were similar for both groups. The mean (± SD) followup was 32 ± 21 months. Survival analysis showed a significantly lower relapse probability (P = 0.02; hazards ratio [HR] = 0.34) and higher event‐free survival (P = 0.02, HR = 0.44) for the 12 CY‐pulse group while the mortality rates were not significantly different (P = 0.47). Conclusion These results suggest that 6 CY pulses are less effective than 12 CY pulses to treat severe PAN and MPA, particularly with respect to the risk of relapses.