Comparable Outcomes Between Unrelated and Haploidentical Stem Cell Transplantation in Adult Patients With Severe Aplastic Anemia.

BACKGROUND: Regarding patients with severe aplastic anemia (SAA) who fail immunosuppressive therapy and lack an HLA-matched sibling donor (MSD), the best alternative donor including unrelated (URD) and haploidentical (HAPLO) donors for allogeneic stem cell transplantation (SCT) remains to be established. METHODS: We analyzed the comprehensive outcomes of 153 consecutive adult SAA patients treated with SCT from alternative donors: 73 HLA-well matched (8/8) URDs (WM-URDs), 34 mismatched (6-7/8) URDs (MM-URDs), and 46 HAPLOs. RESULTS: Neutrophil/platelet engraftments were achieved at a median of 11/15 days for WM-URDs, 13/16.5 days for MM-URDs, and 12/14 days for HAPLOs, respectively. The 3-year overall survival (OS), failure-free survival, cumulative incidence of graft-failure, and transplant-related mortality were statistically not different among the 3 groups: 90.3%, 87.5%, 2.7%, and 9.8% for WM-URDs; 85.3%, 81.7%, 0%, and 14.7% for MM-URDs, and 84.4%, 82.3%, 6.5%, and 11.2% for HAPLOs, respectively. The rates of other complications, including graft-versus-host disease, cytomegalovirus DNAemia, hemorrhagic cystitis, invasive fungal disease, secondary malignancies, and sinusoidal obstruction syndrome, were also statistically not different. Subgroup analysis of the MM-URD group showed that the 3-year OS of patients receiving SCTs from 6/8-URDs were worse than those receiving SCTs from 7/8-URDs (75.0% versus 94.4%, P = 0.26). CONCLUSIONS: There was no significant difference in the SCT outcomes with WM-URDs, MM-URDs, or HAPLO donors. The clinician can make the best choice among these alternative donor sources based on the host/donor features and the urgency of the need for SCT. However, the selection of 6/8-URDs should be avoided due to inferior survival outcomes.