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.

Abstract Idiopathic aplastic anemia is a rare and life-threatening disorder with hematopoietic stem cell transplant (HSCT) from matched sibling donor (MSD) being the standard treatment strategy for young patients. The use of alternative donor transplant (ADT) from a matched unrelated donor (MUD) or HLA haploidentical donor (HID) is not commonly used in the frontline setting. The aim of this systematic review/meta-analysis is to compare ADT as an upfront, rather than delayed, treatment strategy in the absence of a MSD to immunosuppressive therapy (IST) in severe aplastic anemia (SAA). We searched PUBMED/MEDLINE and EMBASE (1998-2019) for studies that compared the outcomes of ADT with IST as upfront therapy in patients with SAA. We included studies with five 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 rate. Five studies met the inclusion criteria and were included in this meta-analysis. The pooled 5-year odd ratio (OR) for OS was statistically significant at 0.44 [95% CI 0.23-0.85] in favor of upfront ADT. Additionally, the survival was compared between upfront versus salvage ADT in six studies. The pooled 5-year OR for OS was statistically significant at 0.31 [95% CI 0.15-0.64] 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 indicated 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.