[Bladder neoplasms and cyclophosphamide. Apropos pf 3 cases amd review of the literature]

We report three new cases of bladder cancer occurring in patients treated by cyclophosphamide (Endoxan): two patients had Waldenström disease and were treated during 7.5 and 7 years respectively (total received dose of 220 and 190 g respectively). The third patient was treated for autoimmune erythroblastopenia and the bladder cancer occurred 5 years after treatment by cyclophosphamide (39 g during 3.3 years). Bladder cancers after cyclophosphamide treatment are generally transitional cell carcinomas. They are observed after an oral treatment, generally given for more than one year. A cumulative dose of more than 20 g is the principal risk factor, with a median interval from treatment to tumor of 7 years. No other risk factor has been identified (tobacco, age, sex, hemorrhagic cystitis). The relative risk of bladder cancer is estimated between 7 and 9, and seems proportional to the cumulative dose of cyclophosphamide. The first hypothesis to explain bladder cancer occurrence is a carcinogenic effect of one of the cyclophosphamide metabolites, acrolein, but the immunosuppressive effect of cyclophosphamide may play a role. The risk of secondary bladder cancer implies to limit the use of cyclophosphamide, particularly in non malignant disease, and to closely watch the patient especially by way of annual cystoscopy.