Cyclophosphamide-Induced Bladder Cancer

TO THE EDITOR: The study by Talar-Williams and colleagues [1] on cyclophosphamide-induced cystitis and bladder cancer in patients with Wegener granulomatosis, which had an extensive follow-up on a large group of patients, may help define the incidence of clinically detectable bladder cancer in these patients. However, the authors' statement that nonglomerular hematuria is a risk factor for this disease may be biased because only patients with nonglomerular hematuria had cystoscopy; the other 72 patients in the cohort did not. Therefore, the true incidence of bladder cancer or cyclophosphamide-induced bladder injury in those 72 patients remains unknown, because in as many as 25% of cases, bladder cancer is not associated with hematuria [2]. If cystoscopy is only done in patients with hematuria and only these patients receive a diagnosis of bladder cancer or cyclophosphamide-induced bladder injury, hematuria will be found as a risk factor for the development of bladder cancer. The only way to find out the incidence of bladder injury in patients treated with cyclophosphamide and its association with hematuria would be to do cystoscopy in all patients, regardless of the occurrence of hematuria.