Although transplants from alternative donors are effective in some patients with leukemia, treatment failure is higher than after HLA-identical sibling transplants. Outcome depends on leukemia state, donor-recipient relationship, and degree of HLA matching. In early leukemia, alternative donor transplants have a more than twofold increased risk of treatment failure compared with HLA-identical sibling transplants. This difference is less in advanced leukemia.

Allogeneic stem cell transplantation (ASCT) has improved leukemia-free survival (LFS) in many but not all patients with acute leukemia. This is an eight-year followup to our previous study showing a survival advantage to patients with an increased cd T cells following ASCT. cd T cell levels were collected prospectively in 153 patients (acute lymphoblastic leukemia (ALL) n ¼ 77; acute myelogenous leukemia (AML) n ¼ 76) undergoing partially mismatched related donor ASCT. Median age was 22 years (1-59), and 62% of the patients were in relapse at transplant. Patient-donor human leukocyte antigen (HLA) disparity of three antigens was 37% in the graft-versushost disease (GvHD) and 29% in the rejection directions. All patients received a partially T cell-depleted graft using T10B9 (n ¼ 46) or OKT3 (n ¼ 107). Five years LFS and overall survival (OS) of patients with increased cd compared to those with normal/decreased numbers were 54.4 vs 19.1%; Po0.0003, and 70.8 vs 19.6% Po0.0001, respectively, with no difference in GvHD (P ¼ 0.96). In a Cox multivariate analysis, normal/decreased cd (hazard ratio (HR) 4.26, P ¼ 0.0002) and sex mismatch (HR 1.45 P ¼ 0.049) were associated with inferior LFS. In conclusion, cd T cells may facilitate a graft-versus-leukemia (GvL) effect, without causing GvHD. Further evaluations of this effect may lead to specific immunotherapy for patients with refractory leukemia.

In patients who receive an allogeneic bone marrow transplant as treatment for acute myelogenous or lymphoblastic leukemia, chronic myelogenous leukemia, or aplastic anemia and who are free of their original disease two years later, the disease is probably cured. However, for many years after transplantation, the mortality among these patients is higher than that in a normal population.

These data indicate superior survival with CY/TBI conditioning, compared with Bu/CY conditioning, for HLA-identical sibling bone marrow transplants in children with ALL.