Infection‐related mortality after HLA‐identical and haploidentical hematopoietic cell transplantation using reduced‐intensity conditioning in an outpatient setting

Background Despite the improvements in supportive care for allogeneic‐hematopoietic cell transplantation (allo‐HCT) recipients, infectious complications and infection‐related mortality (IRM) continue to be a major issue for transplantation centers. Methods We herein report the infectious complications and IRM of 107 and 89 patients that underwent haploidentical (haplo‐HCT) or HLA‐identical HCT at a tertiary referral center during 2013‐2020. Patients in the haplo‐HCT group received post‐transplant cyclophosphamide (PT‐Cy), and all received reduced‐intensity conditioning regimens. Results More haplo‐HCT recipients presented severe infections in the pre‐engraftment period (22.4% vs. 6.7%, p = 0.003). Viral (14.9% vs. 4.5%, p = 0.016) and fungal (12.1% vs. 1.1%, p = 0.003) etiologies were more common in this period in this group. The 100‐day and 2‐year cumulative incidence of IRM was 15% and 21% for the haplo‐HCT and 5.6% and 17% for the HLA‐identical group; no significant differences were observed between the groups. Fungal pathogens mainly contributed to IRM (33.3%). Infections were the most common cause of mortality (40/81, 49.4%). There were significant differences in donor/recipient CMV serostatus between transplant groups (0.002). Conclusions No differences in IRM were observed based on allo‐HCT type, with more haplo‐HCT patients suffering from severe infections in the pre‐engraftment period. Studies to assess future prevention, diagnostic, and treatment strategies to reduce IRM are warranted.