Microtransplantation: A Better Option for AML Patients Without an HLA-Identical Donor?

The optimal therapy for patients with intermediate-risk acute myeloid leukemia (AML) in first complete remission is uncertain. Microtransplantation, the practice of infusing patients with HLA-mismatched peripheral blood stem cells that have been mobilized with granulocyte colony-stimulating factor, preceded by reduced-intensity chemotherapy, may improve survival in this group of patients, but there has never been a comparative study between microtransplantation and reduced-intensity conditioning (RIC) transplantation.

In a presentation at the 2015 ASH Meeting on Hematologic Malignancies, Hui-Sheng Ai, MD, from the Department of Hematology and Transplantation at the Affiliated Hospital of Academy of Military Medical Sciences in Beijing, China, shared results from a study comparing microtransplantation and NSCT in AML patients in first remission.

Dr. Ai and colleagues enrolled 156 intermediate-risk AML patients (age range = 9-59 years):

  • 57 patients who had an HLA-identical donor and were assigned to receive NSCT therapy with graft-versus-host disease (GVHD) prophylaxis
  • 99 patients who had no HLA-identical donor (including 86 family-related, 9 distantly related, and 4 unrelated donors) and were assigned to receive microtransplantation therapy without GVHD prophylaxis

The researchers then calculated the probabilities of 10-year overall survival and leukemia-free survival, finding that rates of both were comparable between the microtransplantation and NSCT groups: 70.7 percent and 61.4 percent for 10-year overall survival, and 59.6 percent and 57.9 percent for leukemia-free survival, respectively (p values were not reported).

The NSCT group was more likely to achieve full donor chimerism (96.5%) and had a higher incidence of GVHD (33.3%) than patients in the microtransplantation group; the microtransplantation group had higher rates of donor microchimerism (75%), slightly higher rates of relapse (32.3% vs. 22.8%), and significantly lower non-relapse mortality (6.9% vs. 19.3%; p=0.021) than the NSCT group.

Dr. Ai did note one factor associated with higher rates of leukemia-free survival and lower relapse: an increase in WT1+CD8+ T cells. Rates of both outcomes for patients with higher counts of WT1+CD8+ T cells, compared with patients with lower counts, were 92 percent versus 40 percent for leukemia-free survival (p=0.003) and 8.0 percent versus 50 percent for relapse (p=0.009).

“These results indicate that, compared with NSCT, microtransplantation produced a comparable survival, less transplantation-related mortality, and avoidance of GVHD,” the authors concluded. Microtransplantation also appeared to overcome the limitations of HLA-barrier, “suggesting [it is] a safe and effective therapy for intermediate-risk AML patients in first remission, particularly for those without an HLA-identical donor.”


Reference

Guo M, Yu C-L, Dong Z, et al. HLA-mismatched microtransplantation vs HLA-matched nonmyeloablative transplantation for acute myeloid leukemia in intermediate-risk: comparable survival but avoids of GVHD. Abstract #5. Presented at the 2015 meeting on Hematologic Malignancies; September 19, 2015; Chicago, IL.

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