Haploidentical hematopoietic stem cell transplantation in adults with Philadelphia-negative acute lymphoblastic leukemia: no difference in the high- and low-risk groups.

Allogeneic hematopoietic stem cell transplantation (HSCT) is the most effective post-consolidation therapy and curative option for adult patients with Philadelphia chromosome-negative (Ph-negative) acute lymphoblastic leukemia (ALL) in first complete remission (CR1). A human leukocyte antigen (HLA)-haploidentical related donor (haplo-RD) is one of the most important alternative sources for those without HLA-identical sibling donor (ISD). The present study aimed to evaluate the outcomes of haploidentical hematopoietic stem cell transplantation (haplo-HSCT) in adult Ph-negative ALL CR1 patients (n = 183). We produced an unmanipulated haplo-HSCT protocol including granulocyte colony stimulating factor (G-CSF) for all donors, intensive immune suppression, anti-thymocyte globulin, and combination of G-CSF-primed bone marrow harvest and G-CSF-mobilized peripheral blood stem cells harvest as the source of stem cell grafts. The median age for high-risk versus low-risk groups were 29 versus 23 years. Three-year incidences of relapse mortality and nonrelapse mortality for high-risk versus low-risk groups were 7.1% versus 11.1% (p = 0.498) and 18.0% versus 16.2% (p = 0.717), respectively. Three-year probabilities of disease-free survival and overall survival for high-risk versus low-risk groups were 67.6% versus 68.2% (p = 0.896) and 74.9% versus 72.7% (p = 0.981), respectively. Multivariate analysis showed that limited cGVHD and a lower pre-HSCT comorbidity burden were associated with better outcomes. In summary, comparable outcomes were observed among high- and low-risk Ph-negative ALL CR1 patients after haplo-HSCT. Haplo-RD could be considered for adults with Ph-negative ALL in CR1 as an important alternative source of donors in cases when no ISD is available.