How should aplastic anemia be managed, considering severity, patient age, and donor availability?

Management of Aplastic Anemia

For newly diagnosed severe aplastic anemia (SAA), patients under age 50 with an HLA-matched sibling donor should receive allogeneic hematopoietic stem cell transplantation (allo-HSCT) as first-line therapy; those without a matched sibling donor should receive immunosuppressive therapy (IST) with horse antithymocyte globulin (ATG), cyclosporine A, and eltrombopag. 1, 2

Treatment Algorithm by Age and Donor Availability

Patients < 50 Years Old with Newly Diagnosed SAA/vSAA

With HLA-Matched Sibling Donor (MSD):

• Proceed directly to allo-HSCT as first-line therapy 1
• This represents the only curative option and provides superior disease-free survival compared to IST
• Conditioning regimen: Cyclophosphamide-ATG (Cy-ATG) for matched sibling transplants 1

Without Matched Sibling Donor:

• First-line IST with horse ATG + cyclosporine A + eltrombopag 2, 3
• The 2026 ASH guidelines specifically recommend adding eltrombopag to standard IST regimens based on improved response rates
• For pediatric patients with ≥9/10 loci-matched unrelated donors (MUD), allo-HSCT may be considered as first-line therapy 1
• For young patients without MSD, haploidentical donor (HID) HSCT is increasingly recommended as first-line therapy 1

Patients 50-60 Years Old

Treatment approach depends on performance status:

• Those with ECOG scores ≤2 and available MSD or MUD should receive allo-HSCT, particularly if IST fails 1
• First-line IST is generally preferred initially for this age group
• Allo-HSCT remains feasible with reduced-intensity conditioning (RIC) regimens for those with good performance status 1

Patients > 60 Years Old

• IST is the primary treatment approach 1
• Allo-HSCT is generally not recommended due to increased transplant-related mortality (TRM)

Management of Refractory/Relapsed Disease

For patients < 50 years who fail IST or relapse:

• Proceed to allo-HSCT using HID, MUD, or cord blood transplant (CBT) 1
• Recent advances with post-transplant cyclophosphamide and reduced-toxicity conditioning have significantly improved outcomes with alternative donors 4
• Disease-free survival after HCT may now be superior to IST, representing a paradigm shift in the field 4

For patients 50-60 years with IST failure:

• MSD or MUD transplantation if ECOG ≤2 1

Conditioning Regimens

For matched sibling transplants:

• Cy-ATG: Cyclophosphamide 200 mg/kg (days -5 to -2) + ATG 11.25-15.00 mg/kg (days -5 to -3 or -2) 1

For unrelated donor transplants:

• FluCy-ATG: Fludarabine 120 mg/m² (days -5 to -2) + Cyclophosphamide 120 mg/kg (days -5, -2) + ATG 1

For haploidentical transplants:

• Modified regimens including mBuCyFluATG or FluCy-ATG with adjusted dosing 1

Supportive Care

The 2026 ASH guidelines recommend:

• Antibiotic prophylaxis in neutropenic patients 2
• Antifungal prophylaxis in high-risk neutropenic patients 2
• Transfusion support as needed

Critical Considerations

Timing is crucial: Patients aged 41-50 years with MSD should undergo allo-HSCT as early as possible (ideally within 6 months of diagnosis) to optimize survival 5. Prolonged time from diagnosis to transplant is associated with worse outcomes.

Donor hierarchy: While MSD remains the gold standard, the gap between MSD and alternative donor outcomes has narrowed significantly with modern techniques 4. The traditional paradigm of reserving alternative donor transplants for IST-refractory patients is being challenged by ongoing clinical trials 4.

Transfusion-dependent non-SAA patients: Should be managed according to SAA guidelines 1

Common pitfall: Delaying transplant evaluation in younger patients without obvious MSD. Early HLA typing of potential alternative donors (including haploidentical family members) is essential, as haploidentical HSCT is now recommended for young patients without MSD 1.