Allogeneic Hematopoietic Cell Transplantation for Acute Myelogenous Leukemia in Remission - a Prospective Comparison of Three Different Donor Groups; Matched Sibling, Matched Unrelated, and Haploidentical Family Donors

Allogeneic hematopoietic cell transplantation (HCT) from HLA-matched sibling (MS) or unrelated donors (MU) is a well-established treatment for patients with intermediate/high-risk acute myelogenous leukemia (AML) in remission. When HLA-matched donors are not available, however, use of haploidentical family (HF) donors for HCT remains controversial.

Therefore, we performed a prospective study, where patients with AML in complete remission (CR) underwent allogeneic HCT according to the donor priority of MS, MU, or HF donors. Conditioning regimen for MS-HCT was busulfan (3.2 mg/kg • 4 days)-cyclophosphamide (60 mg/kg • 2 days) or, for patients >55 years or with co-morbidity, busulfan (3.2 mg/kg • 2 days)-fludarabine (30 mg/m² • 6 days)-Thymoglobulin (1.5 mg/kg • 3 days). Patients undergoing MU- or HF-HCT received busulfan (3.2 mg/kg • 2 days)-fludarabine (30 mg/m² • 6 days)-Thymoglobulin (3 mg/kg • 3 days) (Lee K-H et al; Blood 2011;118:2609-2617; Am J Hematol 2011;86:399-405). Ex-vivo T cell depletion was not performed. GVHD prophylaxis included cyclosporine plus a short course of methotrexate.

Between January 2010 and December 2014, 244 patients enrolled. Of those, 16 patients were excluded from the analysis (12 patients relapsed before HCT; 3 with major protocol violation; and 1 with incomplete data). Of remaining 228 patients, 81 underwent HCT from MS donors, 90 from MU donors, and 57 from HF donors. The donors for MU-HCT were younger and more male-dominant than those for MS- or HF-HCT. The characteristics of patients and their donors were summarized in Table 1.

The median follow-up duration of 164 survivors in the study was 34.7 months (range, 3.7-63.6) after HCT. The donor-group effect on the HCT outcomes was described in Table 2. Patients who underwent MS-HCT showed slightly slower neutrophil engraftment and higher incidence of chronic GVHD. Otherwise, in terms of disease recurrence, NRM, graft failure, EFS, and OS, there was no significant difference according to the donor-type. For AML recurrence, cytogenetic risk was an independent prognostic factors (P =0.003; hazard ratio of low-risk to; intermediate-risk, 1.42; high-risk, 2.53; high-risk with monosomal karyotype, 5.47).

Our study showed that, despite heterogeneity of baseline donor characteristics (age and sex), conditioning regimen, and graft source (bone marrow vs. peripheral blood), overall post-transplant outcomes were similar among recipients from MS-, MU-, and HF-donors. Therefore, for patients with AML in CR but without an HLA-matched donor available, HCT from a haploidentical family member may be considered.