Comparison of Infectious Complications in Patients Receiving High-Dose Cyclophosphamide as GvHD Prophylaxis After Transplantation From A 9/10 HLA-Matched Unrelated Donor with Standard GvHD Prophylaxis After Transplant From A Fully Matched Related Donor.

Background: The aim of this study was to evaluate whether cyclophosphamide administered after allogeneic stem cell transplantation (ASCT) from 9/10 HLA-Matched Unrelated Donors (MMUD) increases the rates of bacterial, fungal, viral infections, complications (hemorrhagic cystitis (HC)), and infection-related mortality compared to allogeneic stem cell transplantation from matched related donors (MRD).

Methods: This is a retrospective multicenter study. 45 MMUD ASCT patients who received posttransplant cyclophosphamide+methotrexate+calcineurin inhibitor compared with 45 MRD ASCT patients who received methotrexate+calcineurin inhibitor.

Results: Although there was a statistically significant prolongation of neutrophil engraftment time in the PTCy arm, there was no statistically significant difference in bacterial infection frequencies between the groups (PTCy; 9 (20%), control; 8 (17.8%), p=0.778). The distribution of CMV infection in the first 100 days was similar (p=0.827), but the distribution of CMV infection rate between the 100th and 365th days was observed more frequently in the control group (p=0.005). HC rates and their grades were similar in both groups (PTCy; 4 (8.8%), control; 6 (13.3%) p=0.502). The rates of VZV infection and invasive aspergillosis were similar in the PTCy and control groups (13.3% in the PTCy and 17.8% in the control group p=0.561). There is also no statistically significant difference in survival analysis (OS, LFS, GRFS, RI, IRM, NRM) between groups. However, the incidence of cGVHD was significantly higher in the control group (P=0.035).

Conclusions: The addition of PTCy to standard GvHD prophylaxis in MMUD ASCT does not lead to an increase in CMV reactivation, bacterial infections, invasive fungal infection, viral hemorrhagic cystitis, or mortality.