Haplotype mismatched transplantation using high doses of peripheral blood CD34+ cell together with stratified conditioning regimens for high-risk adult acute myeloid leukemia patients: A pilot study in a single Korea institution

A total of 11 high-risk Korean acute myeloid leukemia (AML) patients received stem cell transplantation from human leukocyte antigen (HLA) haploidentical donors. Specifically, for eight patients with 2-3 mismatched antigens and bidirectional vectors, we used a newly designed conditioning regimen that consists of total body irradiation, busulfex, ATG, and fludarabine. The median number of CD34+ cells infused was 15.4 × 10⁶/kg (range, 8-21.2). These patients received neither graft-versus-host disease (GvHD) prophylaxis nor post transplantation G-CSF. All of the patients who were followed up for a median of 6 months (range, 17 days-28 months) showed stable primary engraftment and had no acute GvHD or transplant-related mortality for 100 days post transplant. Three patients with high-risk or refractory disease eventually died in relapse, even with GvH-directed NK alloreactivity. However, the patients in complete remission (CR), with the exception of one patient who is alive at 18 months EFS, died at 4, 6, and 8 months post transplantation due to infections that were associated with delayed immune recovery. Our findings suggest that haploidentical transplantation represents a feasible treatment for patients with high-risk AML in CR, provided that a plan for the enhancement of immune recovery is implemented.