Incidence and Predictors of Urotoxic Adverse Events in Cyclophosphamide-Treated Patients With Systemic Necrotizing Vasculitides

Objective. To assess hemorrhagic cystitis and urinary tract cancer incidence and predictors in cyclophosphamide (CYC)-treated patients with systemic necrotizing vasculitis (SNV). Methods. The French Vasculitis Study Group database, which contains longitudinal data on SNV patients, was searched for urinary tract cancer and/or hemorrhagic cystitis occurrences in patients diagnosed as having Wegener's granulomatosis (WG), microscopic polyangiitis, Churg-Strauss syndrome, or polyarteritis nodosa. The observed incidence of urinary tract cancer was compared to the expected incidence in the general population by calculating standardized incidence ratios (SIRs). Relationships between urinary tract cancer and/or hemorrhagic cystitis and 10 variables, including CYC dosage and administration route, were investigated by survival analyses for a nested subgroup of patients for whom detailed information on CYC exposure was available. Results. Among the 805 patients observed over 4,230 patient-years (mean followup 5.3 years), 22 cases of hemorrhagic cystitis and 7 of urinary tract cancer were identified in 27 patients. The SIRs for urinary tract cancer were 5.00 for all patients with SNV (P = 0.001) and 5.96 for patients with WG (P = 0.03). Based on 467 patients with detailed CYC information, cumulative CYC dose (hazard ratio [HR] for 10-gm increments 1.09; P = 0.03), ever-oral CYC administration (HR 5.50; P = 0.001), and WG (HR 2.96; P = 0.01) independently predicted urinary tract cancer and/or hemorrhagic cystitis. According to univariate analyses, smoking (ever) (HR 8.20; P = 0.02) and a prior hemorrhagic cystitis episode (HR 5.20; P = 0.046) significantly predicted urinary tract cancer. Conclusion. Our findings indicate that CYC treatment of SNV is associated with a 5-fold higher risk of developing urinary tract cancer. Urotoxicity risk in SNV is associated with the cumulative CYC dose and its oral administration, and might be higher in WG.