Comparable Outcomes of Sibling and Unrelated Donors Hematopoietic Stem Cell Transplantation for Acute Myeloid Leukemia

Allogeneic hematopoietic stem cell transplantation (alloSCT) is nowadays most frequently applied in patients with acute myeloid leukemia (AML), and it effectively reduces the relapse as its stronger graft-versus-leukemia (GVL) effect, however, the appropriate role and timing of alloSCT in AML are poorly defined. We retrospectively investigated the outcomes of unrelated donor hematopoietic stem cell transplantation (URD-HSCT, n=51; 44 in CR1, 7 beyond CR1) and sibling donor BMT (Sib-HSCT, n=31; 24 in CR1, 7 beyond CR1) for AML between April 1999 and April 2008. The median age of all patients was 27.5 years (range 12–49 years), and HLA high-resolution typing was used for donor-recipient matching with 35 cases of HLA-matched and 16 cases of HLA 1–2 alleles mismatched in URD-HSCT group, while 28 cases of HLA-matched and 3 cases of HLA 1–2 alleles mismatched in Sib-HSCT group. All of the patients were received Bu/Cy or Bu/Cy modified myeloablative conditionging regimen. Mycophenolate mofetil (MMF) combined with CsA and short course MTX were performed to prevent aGVHD and 4 patients in unrelated donor transplant group received additional anti-CD25 monoclonal antibody to prevent severe aGVHD. Hemopoietic recovery and was observed in all patients and the median time to achieve ANC>0.5×10⁹/L was 12.5 days (range 7–22 days), platelets >20×10⁹/L was 15 days (range 9–144 days), and engraftment of neutrophil and platelet did not differ between the two transplant groups. The incidence of aGVHD was significantly higher in URD-HSCT group (54.9% vs 19.4%, p<0.001), however, there was no different of severe aGVHD (13.7% vs 3.2%, p>0.05) and transplant-related mortality (11.8% vs 3.2%, p>0.05) at 100 days between URD-HSCT and Sib-HSCT groups. With a median follow-up of 16.2 months, the 3 years overall survival of the total patients was 73.90±5.11%, and there were no different of disease free survival between AML patients in CR1 and beyond CR1 (69.12% vs 64.29%, p>0.05). Relapse occurred in 15.7% and 9.7% patients following unrelated and sibling donors transplantation respectively, and 3 years disease free survival were 63.85±6.85% and 79.55±7.48% respectively (p>0.05). Based on the data, alloSCT provides a better prospect for cure and would be mostly recommended for patients with AML either in CR1 or beyond CR1, which could be able to improve the leukemia free survival. The outcome of unrelated donor transplantation is comparable to that of sibling donor transplantation for AML. Unrelated donor should be considered in AML patients without a proper sibling donor, especially to patients with unfavorable cytogenetics. MMF combined with CsA and MTX could prevent severe aGVHD efficiently which would reduce the transplant-related mortality in URD-HSCT. At the same time, modifications of supportive care and preparative regimens continue to improve results and extend the application of alloSCT in AML.