Unrelated Transplants for High-risk Adult Acute Lymphoblastic Leukaemia

Abstract

Standard chemotherapy has a poor outcome in adult patients with high-risk acute lymphoblastic leukaemia (ALL). Allogeneic haematopoietic stem cell transplant (alloSCT) is the treatment of choice, and SCT with alternative progenitors should be considered in the absence of a matched sibling donor. There is great heterogeneity in the data on unrelated SCT for adult patients with high-risk ALL. Many studies include both paediatric and adult patients, or provide combined data from ALL and acute myeloid leukaemia (AML) patients. Moreover, the follow-up of the reported series is highly variable, and the definition of high-risk criteria varies from one study to another. The reported disease-free survival (DFS) for adult ALL patients ranges from 30 to 70%, and leukaemia relapse (14–47%) is an important cause of treatment failure. Despite great improvements in recent years, transplant-related mortality (TRM) from unrelated SCT (USCT) remains unacceptably high (29–36%). The human leukocyte antigen (HLA) disparity in the unrelated donor setting with a high incidence of graft-versus-host disease (GvHD) and delayed immunological reconstitution with a high incidence of infectious events in the unrelated cord blood SCT are the most important causes of morbidity and mortality in unrelated transplants. Disease status at transplant and the presence of acute and/or chronic GvHD are the most important factors determining relapse in high-risk ALL adult patients undergoing USCT.