Allogeneic Hematopoietic Cell Transplantation for Acute Myeloid Leukemia When a Matched Related Donor Is Not Available

Abstract

Although for many patients with acute myeloid leukemia (AML) allogeneic hematopoietic cell transplantation (HCT) from a matched related donor provides the best, and sometimes the sole chance for cure, only about 30% of individuals have HLA-matched family members. Fortunately, recent advances on a number of fronts have expanded the acceptable donor pool. With the use of high-resolution typing, HCT outcomes using unrelated donors matched at HLA-A, -B, -C and -DRB1 give results very similar to those expected with matched related donors. A single mismatch, as determined either by low- or high-resolution testing, results in modestly worse outcomes, with mismatches at B or C better tolerated than mismatches at A or DRB1. Initial results of umbilical cord blood transplantation for adults showed a clear association of cell dose and outcome, limiting the procedure to a minority of adults where cord bloods with at least 2.5 or 3 × 10⁷ total nucleated cells/kg could be found. More recently, the use of double cord transplants has shown considerable promise, lowering the risk of graft rejection and possibly the risk of relapse as well. Haploidentical transplantation using T-cell–replete marrow and post-transplant high-dose cyclophosphamide, or T-cell–depleted peripheral blood and marrow containing high doses of CD34⁺ cells is under investigation. Together, these various approaches are broadening the transplant options for patients with AML.