Peripheral Blood Versus Bone Marrow Plus Peripheral Blood Grafts for Haploidentical Transplantation in Severe Aplastic Anemia

Inclusion criteria

• Patients with newly diagnosed or relapsed severe aplastic anemia (SAA) or very severe aplastic anemia (vSAA) according to the Camitta criteria.
• SAA is defined as bone marrow cellularity <25% and at least two of the following peripheral blood criteria: absolute neutrophil count <0.5 × 10^9/L, platelet count <20 × 10^9/L, or reticulocyte count <20 × 10^9/L.
• vSAA is defined as SAA with an absolute neutrophil count <0.2 × 10^9/L.
• Age 18 to 40 years.
• Availability of a haploidentical related donor.
• Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 2.
• Adequate organ function, defined as follows:
• Cardiac function: left ventricular ejection fraction ≥50% and no severe arrhythmia.
• Hepatic function: total bilirubin ≤2 times the upper limit of normal and alanine aminotransferase/aspartate aminotransferase ≤3 times the upper limit of normal.
• Renal function: creatinine clearance ≥60 mL/min.
• No active infection.
• For women of childbearing potential, a negative pregnancy test is required.
• All patients must agree to use effective contraception during the study period.
• Written informed consent provided by the patient or legal representative.

Exclusion criteria

• Presence of hematologic malignancy or myelodysplastic syndrome-related chromosomal abnormalities, such as +8 or del(7q).
• Prior allogeneic hematopoietic stem cell transplantation or prior organ transplantation.
• Availability of an HLA-matched sibling donor.
• Active uncontrolled infection, including unresolved invasive fungal disease, active tuberculosis, sepsis, or other uncontrolled infections.
• Severe comorbidities, defined as a Hematopoietic Cell Transplantation-Comorbidity Index (HCT-CI) score ≥4, or uncontrolled autoimmune disease.
• Donor-related contraindications, including donor age <12 years or >65 years, donor body mass index <18 or >35 kg/m², contraindications to anesthesia, or contraindications to bone marrow harvest.
• Psychiatric illness that prevents cooperation with study procedures, or any condition considered by the investigator to make the patient unsuitable for study participation.