Pb2570: treatment with intravenous cidofovir in hemorrhagic cystitis due to bk virus after allogeneic hematopoietic stem cell transplantation: experience in our center.

Topic: 30. Infections in hematology (incl. supportive care/therapy) Background: Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a potentiall curative option for patients with hematological malignancies, but due to secondary immunosuppression, infections are an important cause of morbidity and mortality. Among viral infections, hemorrhagic cystitis caused by the BK virus (BKV-HC) is worth mentioning. Predisposing factors include: haploidentical transplantation or unrelated donor transplantation, peripheral blood, myeloablative conditioning and the use of cyclophosphamide due to direct damage to the endothelium. Its pharmacological treatment is based on cidofovir presenting clinical and virological efficacy rates between 66 and 86%, but it is also associated with nephrotoxicity in 25-33% of patients. Aims: To analyze demographic and clinical characteristics of hemorragic cystitis due to BK virus infection in stem cell transplantation recipients in our center, and whether our intravenous cidofovir dosing proves to be safe and effective Methods: This is an observational, descriptive, retrospective,single-center study. Patients undergoing allo-HSCT who received at least one dose of intravenous cidofovir for the treatment of BKV-HC, between the years 2017 to 2021, were included. The minimum follow-up time was 6 months from the date of transplantation. Results: Twenty-four patients were included, with a median age at transplantation of 46 years (range 18-68), 14 of whom (58.3%) were male. Acute leukemia (n= 11, 45%) was the main indication for HSCT, 50% (12) were haploidentical and 75% (18) received reduced intensity conditioning. 95% (23) of the patients received post-transplant cyclophosphamide as graft-versus-recipient disease (GVHD) prophylaxis. Despite this, 13 patients (54%) developed GVHD of any grade. Patient characteristics are described in Table 1. The median time to onset of first symptoms of cystitis was 30 days (range 6-59) after allo-HSCT. The most frequent symptom at onset was dysuria, with a severity grade of 2-3 in 92% (22) of the patients. Before treatment 100% of the patients had positive BK virus viral load in urine and 6 (25%) positive serum viral load. Patients received a median of 2 doses (range 1-7) of intravenous cidofovir, and the most used treatment dose was 3mg/kg weekly for two weeks. 18 patients (75%) achieved complete response and the median number of days from treatment initiation to response was 8 (range 1-36). Nephrotoxicity of any grade was detected in 25% (6) of patients. Summary/Conclusion: - Our study seems to support the main known risk factors for the development of BKV-HC - There is no standard and approved treatment protocol for BKV-HC. In our study the use of intravenous cidofovir appears as a feasible treatment option with efficacy rates comparable to what is reported in the literature and acceptable toxicity profile. - Prospective randomized studies are required to describe the optimal treatment strategies for this pathology. Table 1. DEMOGRAPHIC AND CLINICAL CHARACTERISTICS - Age (years), median (range) 46 (18-68) Gender, n (%) Men 14 (58.3) HCT-CI, n (%) 0 1 2 3 4 5 5 (20.8) 10 (41.7) 3 (12.5) 1 (4.2) 3 (12.5) 2 (8.3) CMV D/R, n (%) POS/POS POS/NEG NEG/POS NEG/NEG 19 (79.2) 1 (4.2) 3 (12.5) 1 (4.2) Indication BMT, n (%) AML/ ALL MSD NHL/HL MF 11 (45.8) 4 (16.7) 6 (25) 1 (4.2) Type of donor, n (%) Haploidentical Identical related Not related 12 (50) 7 (29.2) 4 (16.7) Source, n (%) Bone Marrow Peripheral blood 9 (37.5) 15 (62.5) Conditioning, n (%) Myeloablative Reduced intensity 6 (25) 18 (75) Cyclophosphamide pos-BMT, n (%) 23 (95) GVHD, n (%) 13 (54) VOD, n (%) 1 (4.2) Exitus, n (%) TRM Infection Relapse 12 (50) 5 (41.6) 5 (41.6) 2 (16.6) Keywords: Allogeneic bone marrow transplant, Allogeneic stem cell transplant, Bone marrow transplant