Umbilical Cord Blood Transplantation in Children with Acute Leukemia: Impact of Conditioning on Transplantation Outcomes.

The Blood and Marrow Transplant Clinical Trials Network (BMT CTN 0501) randomized children with hematologic malignancies to transplantation with 1 or 2 cord blood units (UCB) between 2006 and 2012. While the trial concluded that survival was similar regardless of number of units infused, survival was better than previously reported. This prompted a comparison of survival of trial versus nontrial patients to determine the generalizability of trial results and whether survival was better because of the trial treatment regimen. During the trial period, 396 recipients of a single UCB unit met trial eligibility but were not enrolled. Trial patients (n = 100) received total body irradiation (TBI) 1320 cGy, cyclophosphamide 120 mg/kg, and fludarabine 75 mg/m2 (TCF). Nontrial patients either received the same regimen (n = 62; nontrial TCF) or alternative regimens (n = 334; nontrial regimens). Five-year survival between trial and nontrial patients conditioned with TCF was similar (70% versus 62%). However, 5-year survival was significantly lower with nontrial TBI-containing (47%; hazard ratio [HR], 1.97; P = .001) and chemotherapy-only regimens (49%; HR, 1.87; P = .007). The results of BMT CTN 0501 appear generalizable to the population of trial-eligible patients. The survival difference between the trial-specified regimen and other regimens indicate the importance of conditioning regimen for UCB transplantation.

Effect of donor-recipient HLA matching at HLA A, B, C, and DRB1 on outcomes after umbilical-cord blood transplantation for leukaemia and myelodysplastic syndrome: a retrospective analysis.

BACKGROUND: The importance of matching at the HLA C locus has not been well defined for unrelated umbilical-cord blood transplantation. The selection algorithm for umbilical-cord blood units generally considers intermediate resolution HLA typing at A and B and allele-level typing at DRB1. We aimed to establish the relative importance of additional matching at HLA C. METHODS: We used Cox regression to assess retrospectively the effect of donor-recipient HLA matching on outcomes of single umbilical-cord blood transplantations for leukaemia and myelodysplastic syndrome. Our primary endpoint was transplant-related mortality. HLA typing was done with molecular techniques with a minimum of intermediate resolution for HLA A, B, and C, and at the allele-level for DRB1. FINDINGS: The median age of our study population was 10 years (range <1-62) and 552 (69%) of 803 patients were aged 16 years or younger at transplantation. Compared with transplantations matched at HLA A, B, C, and DRB1 (n=69), transplant-related mortality risk was higher after transplantations matched at HLA A, B, and DRB1 and mismatched at HLA C (n=23; HR 3·97, 95% CI 1·27-12·40; p=0·018). Transplant-related mortality risk was also higher after transplantations with a single mismatch at HLA A, B, or DRB1 and mismatched at HLA C (n=234; 1·70, 1·06-2·74; p=0·029) compared with transplantations matched at HLA C with a single mismatch at HLA A, B, or DRB1 (n=127). Assessing the overall effect of HLA disparity on transplant-related mortality, risks were higher with units mismatched at two (n=259; 3·27, 1·42-7·54; p=0·006), three (n=253; 3·34, 1·45-7·71; p=0·005), or four (n=75; 3·51, 1·44-8·58; p=0·006) loci compared with matched units (n=69). INTERPRETATION: Our data suggest that the present strategy for umbilical-cord blood unit selection should be reassessed; matching at HLA C for units that are matched at HLA A, B, or DRB1 or in the presence of a single locus mismatch at HLA A, B, or DRB1 should be included to minimise mortality risks. FUNDING: National Cancer Institute, National Heart Lung and Blood Institute, National Institute for Allergy and Infectious Diseases, Leukemia and Lymphoma Society, US Department of the Navy, Children's Leukemia Research Association, and INSERM.