Post Transplantation Cyclophosphamide (PTCY) Is Associated with Increased Risk of BK Virus-Associated Hemorrhagic Cystitis (BKHC) in Patients Undergoing Allogeneic Hematopoietic Stem Cell Transplant (HSCT)

Introduction BK virus hemorrhagic cystitis is a well-recognized complication in patients undergoing allogeneic HSCT and is associated with significant morbidity. PTCY has been used for GVHD prophylaxis in patients undergoing haploidentical or mismatched unrelated donor HSCT. We hypothesized that PTCY is associated with increased incidence of HC associated with BK virus. Objectives • To identify the risk factors for developing BKHC in allogeneic HSCT • To assess the effect of PTCY in development of BKHC in patients with myeloablative (MA) regimen containing total body irradiation (TBI) • To evaluate the risk of concurrent CMV infection and BKHC in allogeneic HSCT with MA conditioning regimen Methods We identified 116 consecutive patients who underwent allogeneic HSCT at our institution between January 2015 and July 2018. The MA regimen (n=42) consisted of fludarabine 50 mg/m2/day IV for 5 days and busulfan 3.2 mg/kg/day IV for 4 days with or without TBI of 200 cGy/day for 2 days (FBT or FB4). The reduced intensity conditioning (RIC) regimen (n=74) consisted of fludarabine 30 mg/m2/day IV for 5 days and busulfan 3.2 mg/kg/day IV for 2 days (FB2). In terms of GVHD prophylaxis all recipients except those undergoing haploidentical and mismatched unrelated transplant received Thymoglobulin 2 mg/kg/daily IV days -2, -1 and 0 (n=80). Recipients of haplo- related and mismatched unrelated donor transplantation received cyclophosphamide 50 mg/kg IV on day +3 and +4 along with Mesna (n=36). All patients received post-transplant immunosuppression with Tacrolimus and Mycophenolate Mofetil. Patients with urinary symptoms were tested for BKV in urine by PCR. Results The median age of patients was 56 years (range 20–76). A total of 31% of patients (n=13) received PTCY in FBT group which was similar to 31% of patients (n=23) in FB4-FB2 (p=0.98). Overall 21.5% patients were diagnosed with BKHC. The patients who received ATG, the incidence of BKHC was 27.5% in FBT group and 11.7 % in FB4-FB2 (p=0.073). The patients who received PTCY, the incidence of BKHC was significantly increased to 69.2% in FBT vs 9% in FB4-FB2 (p=0.0001). The risk of developing concurrent CMV viremia and BKHC was increased to 10.3% in FBT compared to 5.8% in FB2-FB4 (p=0.662). The patients who received PTCY following FBT, the incidence of concurrent CMV viremia and BKHC was increased to 23.1%. as compared to 0% with FB2-FB4. Conclusion Our result shows the addition of PTCY to TBI containing regimen significantly increased the incidence of BKHC. We did not observe increase in the incidence of BKHC in patients receiving PTCY with FB2 or FB4 regimens. Our study revealed an increased incidence of concurrent BKHC and CMV viremia in patients receiving PTCY with FBT which could be due to increased immunosuppression. Our findings suggest that using PTCY as GVHD prophylaxis in patients undergoing MA conditioning regimen including TBI is a risk factor for BKHC.