Selection of Suitable Alternative Donor in the Absence of Matched Sibling Donor: A Retrospective Single-Center Study to Compare between Haploidentical, 10/10 and 9/10 Unrelated Donor Transplantation

Finding a suitable donor at the optimal time is one of the most challenging issues in many transplant centers. We evaluated the clinical outcomes of 248 patients with acute leukemia and without matched sibling donors (MSD) who underwent alternative transplantation, including haploidentical (n=118), 10/10 matched unrelated (MUD, n=91), 9/10 mismatched unrelated (MMUD, n=21), and 9/10 mismatched related (MMRD, n=18) between January 2010 and November 2019 in our center.

The myeloablative conditioning regimen was used in most of the patients. Both post-transplant cyclophosphamide (40mg/kg at +3, +4) and pre-transplant ATG were used in most of Haploidentical transplantations. Patients with unrelated donors received ATG as a part of the conditioning regimen.

The median follow-up was 31.83 months. No significant difference in probability of 3-year leukemia- free survival (LFS) and overall survival (OS) as well as 3-year relapse incidence (RI) were noted between donor sources.A significant difference was found in the 3-year cumulative incidence (CI) of non-relapse mortality (NRM) among the donor sources: 37.89%, 24.20%, 24.30%, and 11.48%, for Haplo, 9/10 MMUD, 10/10 MUD, and 9/10 MMRD (p=0.02). Using the multivariable Cox model, the advanced age of patients and Major-ABO mismatched, were two risk factors independently associated with lower OS and DFS as well as higher NRM, whereas male donor and AML disease compared to ALL were associated with a better OS and DFS.

Given that no significant differences were observed in the overall outcome of Haplo with other alternative transplantations, suggesting that Haploidentical transplantation is a suitable, accessible, and inexpensive option.