Aplastic anemia (AA) is a bone marrow failure disorder characterized by pancytopenia and hypoplastic bone marrow caused by the decrease of hematopoietic stem cells. The pathogenesis of AA is complex and involves an abnormal hematopoietic microenvironment, hematopoietic stem cell/progenitor cell deficiencies and immunity disorders.
Currently, the standard treatment for AA includes immunosuppressive therapy (IST) based on anti-thymocyte/lymphocyte globulin (ATG/ALG) and cyclosporine A (CsA) or hematopoietic stem cell transplantation (HSCT). Although HLA-identical sibling allogeneic hematopoietic stem cell transplantation is considered the preferred transplant option for patients with severe aplastic anemia (SAA), only less than 30% of patients have an available HLA-matched sibling donor. In recent years, haploidentical hematopoietic cell transplantation (Haplo-HCT) has developed rapidly and has become an important alternative. However, graft failure and graft-versus-host disease (GVHD) remain significant factors limiting its efficacy.
Umbilical cord blood (UCB) contains a diverse population of hematopoietic stem cells. Compared with other sources, cord blood-derived hematopoietic stem cells are more primitive, more viable, and possess higher proliferative capacity. Therefore, cord blood transplantation, with its notable clinical therapeutic effects, has become an effective and reliable alternative to peripheral blood or bone marrow transplantation.
Currently, some transplant centers worldwide have adopted the coinfusion of UCB units with haplo-HCT (haplo-cord HCT) achieving preliminary efficacy in promoting engraftment and reducing the incidence of GVHD. A retrospective comparative study of haplo-cord HCT versus IST in patients with SAA identified haplo-cord HCT as the sole independent predictor for superior health-related quality of life (HRQoL) (P \< 0.0001).
Based on existing research and clinical experience, this study plans to investigate and further evaluate the safety and efficacy of haplo-cord HCT in the treatment of aplastic anemia. Primary endpoints will include overall survival, engraftment rate, disease-free survival, incidence of GVHD, CMV/EBV reactivation rate, donor chimerism dynamics, and immune reconstitution.
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Haploidentical hematopoietic cell transplantation combined with unrelated cord blood stem cells
Procedure/Surgery1\. Donor Stem Cells Infusion (Haploidentical hematopoietic cell transplantation combined with unrelated cord blood stem cells) Day 0: Intravenous infuse a single unit of unrelated cord blood stem cells( TNC≤2×10⁷/kg, CD34+ cells≤0.8×10⁵/kg, HLA match≥5/10 loci, and either matched ABO type or a cord blood unit of type O). This is followed, 6 hours after the cord blood infusion, by the infusion of donor haploidentical stem cells (TNC≥8×10⁸/kg, CD34+ cells≥4.0×10⁶/kg, and HLA match≥6/12 loci). 2. Conditioning Regimen: Day -7 to Day -6: Busulfan (Bu) 3.2mg/kg/day; Day -5 to Day -2: Cyclophosphamide (CTX) 160-200mg/kg. 3. Graft-versus-Host Disease Prophylaxis Regimen: Starting on the day before transplantation (Day -1): Cyclosporin A (CsA) 3mg/kg/day; Day +1 to Day +28: Mycophenolate Mofetil (MMF) 600mg/㎡/12h. 4. Infection Prophylaxis Regimen: Day -7 to Day -3: Ganciclovir (GCV): 5mg/kg/12h; Starting two days before transplantation (Day -2):Aciclovir (ACV): 250mg/㎡/8h.
Haploidentical hematopoietic cell transplantation
Procedure/Surgery1\. Donor Stem Cell Infusion (Haploidentical hematopoietic cell transplantation) Day 0: Intravenous infuse of donor haploidentical stem cells (TNC≥8×10⁸/kg, CD34+ cells≥4.0×10⁶/kg, and HLA match≥6/12 loci). 2. Conditioning Regimen: Day -7 to Day -6: Busulfan (Bu) 3.2mg/kg/day; Day -5 to Day -2: Cyclophosphamide (CTX) 160-200mg/kg. 3. Graft-versus-Host Disease Prophylaxis Regimen: Starting on the day before transplantation (Day -1): Cyclosporin A (CsA) 3mg/kg/day; Day +1 to Day +28: Mycophenolate Mofetil (MMF) 600mg/㎡/12h. 4. Infection Prophylaxis Regimen: Day -7 to Day -3: Ganciclovir (GCV): 5mg/kg/12h; Continuous medication starting from two days before transplantation (Day -2): Aciclovir (ACV): 250mg/㎡/8h.
Overall survival rate
We estimated OS from the time of transplant until the date of death of any cause or last follow-up for patients still alive.
The cumulative incidence of neutrophil engraftment and platelet engraftment
Neutrophil and platelet engraftment is defined as the first occurence of 3 consecutive days with an absolute neutrophil count of at least 0.5x10⁹/L and a platelet count of over 20x10⁹/L/L for 7 consecutive days without transfusion support.
Disease Free Survival
We defined DFS as the time from the initiation of transplant to the occurrence of any treatment failure event (including graft failure or disease relapse requiring therapeutic intervention), or death from any cause, whichever occurred first. Patients who were alive and event-free at the last follow-up were censored.
The cumulative incidence and grade of graft-versus-host disease (GVHD)
Graft-versus-host disease (GvHD) is a medical complication following the receipt of transplanted tissue from a genetically diferent person.
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