EBMT 2025 | Factors to consider when selecting a patient with aplastic anemia for transplantation

When selecting a patient with severe aplastic anemia for allogeneic transplant, several factors must be carefully considered to optimize outcomes and minimize risks. 

So these key factors in patient selection for transplantation are the disease severity, so patients with severe aplastic anemia or very severe aplastic anemia are the primary indications for allo. 

Also, patient age is very important. So, younger patients, this is defined as ages below 40 or 50 years old, with an available matched sibling donor, are the first-line candidates for allo. Other patients or those without a matched sibling donor may receive immunosuppressive therapy first. And for patients with ages above 50, allo is considered case-by-case, balancing frailty, comorbidities, and also a donor option. 

So, also, it’s important to consider the donor availability and the HLA matching. So, the preferred donor hierarchy is that HLA-matched sibling donors are the ones who provide the best survival and lowest transplant-related complications. The matched-unrelated donors should be considered if a matched sibling donor is unavailable. With respect to the mismatched-unrelated donors or haploidentical donors, this is an alternative when a matched-related donor is not available, often requiring post-transplant cyclophosphamide for GvHD control. And umbilical cord blood is less commonly used, but remains an option, especially in pediatric patients. 

With respect to the timing of transplantation, early transplantation improves survival and reduces complications. And delayed transplant, especially after failed immunosuppressive therapy, may increase the risk due to the transfusion burden and also infections. It’s important to consider the comorbidities pre-transplant and also the performance status, so patients should be with a Karnofsky performance status above 70%, more or less. Also, the comorbidity index, because higher scores predict worse outcomes. It’s important to consider if it exists pre-existing infections are present, such as active fungal or viral infections that can increase the post-transplant mortality risks. 

We have to consider also the previous treatment and the history of transfusions. So patients failing immunosuppressive therapy are transplant candidates. Those with transfusion burden with multiple red cells or platelet transfusions increase alloimmunization risk and may lead to graft failure. And also the clonal evolution, so patients developing MDS or AML may require early transplantation. 

Also, we have to consider the conditioning regimen tolerance. So, standard regimens include fludarabine and cyclophosphamide with antithymocyte globulin (ATG), often also with total body irradiation (TBI), especially in haplo and mismatch-unrelated transplants. Normally, we use reduced intensity conditioning and this may be used also in older or frail patients to reduce the toxicity. 

So in conclusion, I would say that the decision to proceed with transplantation in aplastic anemia is balanced between the disease severity, the donor availability, the patient’s fitness, and the timing. So matched sibling donor transplants remain the gold standard while matched unrelated donors, mismatched, and haploidentical donors are options, expanding access for those without a matched sibling And I think it’s important that early referral to a transplant center and careful patient selection are crucial to achieving the best outcomes.

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