Have haploidentical transplants replaced umbilical cord transplants for acute leukemias?

Haploidentical stem cell transplantation (Haplo SCT) and umbilical cord blood stem cell transplantation (UCB SCT) have emerged over the past two to three decades as viable sources of alternative donor SCT when a human leukocyte antigen matched donor is not available. However, which of these two donor types is optimal for patients with leukemia in need of allografting is unknown.

For patients with acute leukemia, results of UCB SCT have been improved by the use of double umbilical cord units and emerging ex-vivo expansion technologies. However, the costs associated with procuring double cord units and high transplant-related mortality due to delayed immunological reconstitution and infections, particularly in adult patients, remain a problem. Recently, Haplo SCT has become an increasingly utilized alternative donor source. While improvements of ex-vivo T-cell depletion platforms continue, emergence of T-cell-replete platforms, such as the use of post-transplantation cyclophosphamide (PTCy), is increasingly being utilized in treating acute leukemia patients. PTCy-based Haplo SCT is gaining popularity among transplant clinicians due to its relatively easy learning curve, low cost, low incidence of graft-versus-host disease, and favorable survival in acute leukemia patients.

The clinical question of whether Haplo SCT should replace UCB SCT needs to be answered by ongoing randomized trials. However, the rapidly increasing adoption of Haplo SCT worldwide as the viable alternative for patients without a human leukocyte antigen-matched donor has seemingly addressed the question ahead of scientific judgment.