Effect of Cyclophosphamide on Hemorrhagic Cystitis Following Haploidentical Related Compared to Matched Related/Unrelated Donor Hematopoietic Stem Cell Transplantation: A 7-Year Tertiary Center Analysis

Introduction Hemorrhagic cystitis (HC) is a serious and common complication of hematopoietic cell transplantation (HCT) affecting both allogeneic (alloHCT) and haploidentical HCT recipients.The aims of this study were to determine the incidence, risk factors, severity, morbidity pattern and toxicity of treatment, and outcome of HC in recipients of HSCT at a single tertiary transplant center. Methods We analyzed all patients undergoing haploidentical (haploHCT) or MRD/MUD alloHCT at our bone marrow transplant unit from September 2012 through June 2019. In alloHCT group, 70% (n=205) of the patients received myeloablative conditioning consisted of Cy and only six patients (2%) received identical GVHD prevention with a post-transplant Cy-based regimen. Conversely; in haploHCT group, use of Cy-containing preparative regimen was not often (22.9 % (n=8)) but 77.1% (n=27) of the patients received post-transplant Cy. Results A total of 328 HSCTs were performed during the study period, of which 169 (51.5%) alloHSCT from MUD, 124 (37.8%) alloHCT from MRD and 35 (10.7%) haploHCT. Baseline characteristics of the patients were similar among two groups with regarding to age, diagnosis, disease status and intensity of conditioning. Hemorrhagic cystitis was diagnosed in 78 of 328 patients (23.8%) with a median follow up 7.4 months. Disease status at transplant, recipient age, cytomegalovirus antigenemia and the intensity of conditioning regimen were not associated with the development of HC. The incidence of HC was significantly higher in patients who received grafts from haploidentical donors compared to those receiving grafts from MRD/MUDs (54.3% (n=19) vs 20.1% (n=59), p Conclusion Conditioning regimen is an important factor in the development of HC and its mechanism has been well described. In our study, we could not demonstrate the increased HC risk of conditioning regimens including cyclophosphamide. We also showed that cyclophosphamide in MAC had similar HC risk compared with RIC containing cyclophosphamide.In this retrospective analysis, BK virus was detected 45 patients out of 78 patients with HC and BK viruria was not associated with HC severity.