2660. Infection Complications Following Mismatched Allogeneic Hematopoietic Cell Transplantation

BACKGROUND: The use of haploidentitical or HLA mismatched unrelated donors permits allogeneic hematopoietic cell transplantation (HCT) in individuals with otherwise no donors available. Post-transplantcyclophosphamide(PTCy) is used for prevention graft-vs.-host disease (GVHD) in recipients of mismatched donors. We hypothesized that type and incidence of infectious complications following allogeneic HCT would vary according to the type of transplant. METHODS: We systematically assessed viral kinetics and reactivation rates for cytomegalovirus (CMV) in a prospective cohort of mismatched unrelated donor (MMUD) HCT recipients who had PTCy at our center (April 2017–March 2019). In addition, we evaluated the incidence of invasive aspergillosis (IA), invasive candidiasis (IC), bloodstream infection (BSI), pneumonia, Clostridium difficile (CDI), and community-acquired respiratory virus. Haploidentical donor and anti-thymocyte globulin (ATG) treated MMUD recipients were served as historical control groups. RESULTS: A total of 81 patients were analyzed in 3 groups (Table 1): PTCy MMUD (group 1; n = 22), ATG MMUD (group 2; n = 40) and haploidentical (group 3; n = 19). Whereas the 1 year incidence of CMV viremia was similar across groups, the rate of clinically significant (requiring preemptive therapy) CMV viremia was lower in group 1, compared with groups 2 and 3 (18 vs 53%; P = 0.02). The 1 year incidence of CDI was 47% in group 3 vs. 18% in groups 1 and 2 (P = 0.01). There was no significant difference in the incidence of IA (5–18%), pneumonia (30–42%), BSI (32–55%) and CARVs (28–53%) between groups. There were no cases of IC in this cohort. 1 year infection attributable mortality was lower in group 1 (figure), compared with groups 2 and 3, (9%, 62% and 39%, respectively; P = 0.005). CONCLUSION: Compared with ATG MMUD and haploidentical donor, PTCy MMUD HCT was associated with lower incidence of clinically significant CMV and lower infection attributable mortality. These findings might be related to the contemporary prophylactic strategies used in this patient population. Larger studies are needed. [Image: see text] [Image: see text] DISCLOSURES: All authors: No reported disclosures.