Late-Onset Hemorrhagic Cystitis in Children After Hematopoietic Stem Cell Transplantation (HSCT) for Thalassemia and Sickle Cell Anemia: A Prospective Evaluation of Polyoma (BK) Virus Infection and Treatment with Cidofovir (CDV).

Hemorrhagic cystitis (HC) is a significant cause of morbidity after allogeneic HSCT. BK virus infection has been associated with development of HC after HSCT, however most studies detected the virus at the time of cystitis, therefore not allowing estimation of the relationship between BK reactivation and HC. Furthermore little is known about development of late-onset HC in children following HSCT, its association with BK virus and treatment with Cidofovir. Therefore we prospectively investigated BK virus reactivation in pts receiving HSCT from HLA-identical related donors, risk factors for development of HC and treatment efficacy with CDV.

117 pts with thalassemia (n=107) and sickle cell anemia (n=10) with median age of 9 years (range, 1.7-17) were enrolled in this study. All pts received BUCY ± Thiotepa containing conditioning regimens. GVHD prophylaxis was cyclosporine and short MTX ± Thymoglobulin-ATG (in 26 pts). Before August 2006 qualitative BK-PCR was performed on urine samples in pts with HC. Since then we prospectively performed qualitative and quantitative PCR on blood and urine samples collected before conditioning regimen and weekly thereafter until at least 100 days post transplant in 64 pts. The quantitative BK virus assay was performed with Real Time Alert Q-PCR-Nanogen kit. Risk factors for the development of HC were evaluated on univariate and multivariate analysis using cumulative incidence curves and Competing risk regression analysis respectively. The cumulative incidence of HC was estimated considering death without HC as competing event. Nineteen pts with HC were given CDV at 1.5 mg/kg/day 3 times/week (n= 10) or 5 mg/kg/week (n=9).

60 out of 64 pts (94%) had at least 1 positive and 52 of them (81%) 2 or more positive samples for BK viruria. 34 pts (53%) showed al least 1 and 18 of them (28%) 2 or more positive samples for BK viremia. The number of viral copies varied from <556 to >55 million copies. Median time to platelet engraftment was 23 days (range,8-163) and median number of platelets at onset of HC was 81×10⁹/l (range, 2-274 ×10⁹/l). Thirty pts (26%) developed clinically significant (grade 2 to 4) HC within 1 year after HSCT at a median of 38 days (range, 13- 114). All pts with HC had BK viruria. Coexisting viral infections were found in 3 pts: CMV in 2 and adenovirus in 1. The severity of HC was grade 2 in 24 pts, grade 3 in 2 and grade 4 in 4. The 4 pts with grade 4 HC had moderate or severe hydronephrosis along with partial ureteral obstruction which necessitated ureteral stent placement. The cumulative incidence of grade 2 or 3-4 HC was 21%(95% CI 13%-28%) and 5%(95%CI 2%-10%) respectively. In univariate analysis the use of ATG, peak BK viruria, GVHD and age >8 years were associated with HC. Multivariate analysis confirmed the prognostic importance of ATG (HR=10.5; p=0.001), peak BK viruria >100,000 copies (HR=6.2; p=0.004), and acute GVHD (HR=5.3; p=0.007), but not age for HC development. The cumulative incidence of HC in pts who had 2 adverse factors was 64%, compared with 31% (or 53%) and 10 % who had either one (GVHD or ATG) or none of these factors (p<0.0001). However, there were 10 pts who had at 2 or more time points BK viruria >6 millions copies without developing HC. With a median follow-up among survivors of 35 months (range, 5-61) HC did not have a significant impact on survival.

Both dosing schedules of CDV were well tolerated and no cases of dose-limiting nephrotoxicity were observed. The median duration of HC was 17 days (range 9-53). The median duration of therapy was 27 days (range,21-180) with a median of 9 doses given (range,6-22). All pts had clinical response but only 6 pts (32%) had microbiological response at 2 weeks after therapy. None of these patients cleared BK viruria when a complete clinical response was achieved. The median time from clinical response to BK viruria clearance was 74 days (range, 14-176). Ten pts with grade 2 and one with grade 3 HC occurred before prospective trial of CDV had spontaneous resolution of HC. The median duration of HC in these pts was similar to those treated with CDV.

BK viruria is common after HSCT and high viral load is a risk factor for HC. However, even higher-level BK replication alone is not sufficient to cause HC. Coexisting factors such as the use of ATG and GVHD significantly contribute to the development of HC. Cidofovir may have some activity against BK virus-related HC, although our data showed that spontaneous resolution of HC could also occur.

No relevant conflicts of interest to declare

Off Label Use: Cidofovir as antiviral drug for treatment of BK virus-related hemorrhagic cystitis.