Haploidentical Donor versus Mismatched Unrelated Donor in Reduced-Intensity Conditioning Stem Cell Transplantation: A...

Area of Science:

• Hematology
• Immunology
• Oncology

Background:

• Optimal donor selection for allogeneic stem cell transplantation (HSCT) is critical, especially when matched donors are unavailable.
• Haploidentical (HAPLO) and mismatched unrelated donor (MMUD) HSCT are increasingly considered alternatives.
• Reduced-intensity conditioning (allo-RIC) and various graft-versus-host disease (GVHD) prophylaxis strategies are employed.

Purpose of the Study:

• To compare graft-versus-host disease and relapse-free survival (GRFS) between HAPLO and MMUD HSCT.
• To evaluate outcomes based on different GVHD prophylaxis strategies, specifically post-transplant cyclophosphamide (PTCy).
• To assess secondary endpoints including survival, mortality, relapse, and GVHD incidence.

Main Methods:

• Retrospective analysis of first allo-RIC HSCT from January 2012 to March 2022 across 12 centers.
• Cohorts included HAPLO (PTCy-based GVHD prophylaxis) and MMUD (PTCy-based or alternative prophylaxis).
• Comparison of GRFS, overall survival (OS), disease-free survival (DFS), non-relapsed mortality (NRM), and GVHD rates.

Main Results:

• Two-year GRFS was comparable across HAPLO (47%), MMUD-PTCy (52%), and MMUD-OTHERS (43%) groups (p=0.8).
• Relapse was the primary cause of GRFS failure in MMUD groups, while NRM predominated in the HAPLO group.
• PTCy prophylaxis was associated with lower moderate/severe chronic GVHD incidence (12.2% HAPLO, 11% MMUD-PTCy vs. 21.7% MMUD-OTHERS).

Conclusions:

• HAPLO and MMUD HSCT utilizing PTCy achieve comparable GRFS, OS, relapse, and NRM.
• MMUD without PTCy is associated with a higher incidence of moderate-to-severe chronic GVHD.
• PTCy-based GVHD prophylaxis is recommended when a fully matched donor is unavailable.