Endovesical instillation of Cidofovir in the treatment of BK polyomavirus hemorrhagic cystitis after allogeneic hematopoietic cell transplantation

Background: Hemorrhagic cystitis (HC) with BK polyomavirus (BKPyV) is a common complication after allogeneic hematopoietic cell transplantation (alloHCT) that may lead to severe discomfort for the patient and significant morbidity (urinary obstruction, increased transfusion requirements and prolonged hospitalization). So far, there is no clear consensus on how to manage this complication. Patients and methods: Here, we report a single-center case series of 9 patients (4 children and 5 adults) treated with cidofovir endovesical (EV) instillation(s) for BKPyV-HC after alloHCT. EV Cidofovir was administered at a dose of 5 mg/kg, for 1 to 3 instillations (with a minimum delay between 2 successive doses of 5 days). Results: Eight out of the 9 treated patients with EV Cidofovir achieved a complete resolution of HC after 1–3 instillation(s), without recurrence of symptomatic infection within the next 3 months. Only 1 adult patient did not improve after treatment and developed severe morbidity (emphysematous cystitis). Conclusion: Although this single-center case series of EV cidofovir for BKPyV HC after alloHCT shows encouraging results, only large prospective studies will definitively establish the effectiveness of this therapy.