Upfront Alternative Donor Transplant versus Immunosuppressive Therapy in Patients with Severe Aplastic Anemia Who Lack a Fully HLA-Matched Related Donor: Systematic Review and Meta-Analysis of Retrospective Studies, on Behalf of the Severe Aplastic Anemia Working Party of the European Group for Blood and Marrow Transplantation.

Idiopathic aplastic anemia is a rare and life-threatening disorder, and hematopoietic stem cell transplantation (HSCT) from a matched sibling donor (MSD) is the standard treatment strategy for young patients. Alternative donor transplantation (ADT) from a matched unrelated donor or an HLA haploidentical donor is not commonly used in the frontline setting. This systematic review/meta-analysis was conducted to compare ADT as an upfront, rather than delayed, treatment strategy in the absence of an MSD to immunosuppressive therapy (IST) in severe aplastic anemia (SAA). We searched PubMed/MEDLINE and Embase (1998 to 2019) for studies that compared the outcomes of ADT with IST as upfront therapy in patients with SAA. We included studies with 5 patients or more in each arm. Studies that included patients with inherited forms of bone marrow failure syndromes were excluded. The primary outcome was the 5-year overall survival (OS) rate. Five studies met the inclusion criteria and were included in this meta-analysis. The pooled 5-year odds ratio (OR) for OS was statistically significant at 0.44 (95% confidence interval [CI], 0.23 to 0.85) in favor of upfront ADT. In addition, survival was compared between upfront ADT versus salvage ADT in 6 studies. The pooled 5-year OR for OS was statistically significant at 0.31 (95% CI, 0.15 to 0.64) in favor of upfront ADT. Although this analysis has some limitations, including the retrospective nature of the included studies, the lack of ethnic diversity, the predominantly pediatric population, and the relatively suboptimal IST regimen used in some of the studies, it indicates that upfront ADT is a potential alternative treatment option in young and pediatric SAA patients who lack an HLA identical sibling donor, particularly when optimal IST is not available. © 2021 American Society for Transplantation and Cellular Therapy. Published by Elsevier Inc.