Results of unrelated cord blood transplantation (UCBT) in childhood acute myeloid leukemia (AML) have not been previously reported. We analyzed 95 children receiving UCB transplants for AML (20 in first complete remission [CR1], 47 in CR2, and 28 in more advanced stage). Poor prognosis cytogenetic abnormalities were identified in 29 cases. Most patients received a 1 or 2 HLA antigens-mismatched UCB transplants. The median number of collected nucleated cells (NCs) was 5.2 ؋ 10 7 / kg. Cumulative incidence (CI) of neutrophil recovery was 78% ؎ 4%, acute graftversus-host disease (GVHD) was 35% ؎ 5%, and 100-day transplantation-related mortality (TRM) was 20% ؎ 4%. In multivariable analysis, a collected NC dose higher than 5.2 ؋ 10 7 /kg was associated with a lower 100-day TRM. The 2-year CI of relapse was 29% ؎ 5% and was associated with disease status. The 2-year leukemia-free survival (LFS) was 42% ؎ 5% (59% ؎ 11% in CR1, 50% ؎ 8% in CR2, and 21% ؎ 9% for children not in CR). Children with poor prognosis cytogenetic features had similar LFS compared with other patients (44% ؎ 11% vs 40% ؎ 8%). In CR2, LFS was not influenced by the length of CR1 (53% ؎ 11% in CR1 < 9.5 months compared with 50% ؎ 12% in later relapses). We conclude that UCBT is a therapeutic option for children with very poorprognosis AML and who lack an HLAidentical sibling. IntroductionBone marrow transplantation (BMT) from an HLA-matched sibling or unrelated donor plays a major role in the treatment of children with relapsed acute myeloid leukemia (AML). [1][2][3][4][5][6] However, although there are currently more than 8 million donors registered in marrow donor registries around the world, a substantial proportion of children who lack a sibling donor will never undergo BMT from an HLA-matched unrelated donor either because such a donor cannot be found or because the time to identify a donor is too long. Moreover, for those children who received unrelated bone marrow transplants, increased HLA disparity adversely affects survival because of high risk of graft-versus-host disease (GVHD) and opportunistic infections. [7][8][9] The use of haploidentical family donors provides a potential source of hematopoietic stem cells for children who lack both a sibling and an unrelated donor. [10][11] T-cell depletion of the graft can in part overcome the risk of severe GVHD, but it substantially increases the risk of severe and prolonged posttransplantation immunodeficiency.Hematopoietic stem cells from an unrelated cord blood (UCB) transplant can restore hematopoiesis and immune function after a myeloablative conditioning regimen, even if the graft is not perfectly HLA identical to the recipient. [12][13][14][15] This important medical advance led to the establishment of large cord blood banks that made possible the use of UCB to provide transplants for patients who lack a conventional related or unrelated donor. In addition, UCB offers the advantage of significantly faster availability of banked cryopreserved UCB units compared with the availability of u...

Delayed hematologic recovery is common after unrelated donor umbilical cord blood transplants (UCBT). Clinically it is important to quickly differentiate slow engraftment from graft failure (GF). We report the engraftment data on 110 pediatric UCBT recipients. By day 28, 71 patients achieved an ANC 40.5 Â 10 9 per liter, and 6 others died early without recovery. Of the remaining 33 patients who were still neutropenic, 20 eventually attained donor myeloid recovery, 3 died of transplant-related complications or recurrent leukemia and 10 survived without donor-derived hematopoiesis. These patients received a second UCBT 33-95 days after the first transplant, after additional immunosuppression. One patient died early, the remaining nine patients were engrafted; eight demonstrated complete, and one mixed, donor chimerism (with subsequent graft loss). Acute GVHD developed in three, and chronic GVHD in six of the eight engrafted patients. Two patients developed EBV-lymphoproliferative disorder. Infections, especially viral, were common and protracted. Six of 10 patients are alive, 165-1375 (median 1147) days after second UCBT. Chimerism studies correlated with subsequent engraftment course. Any result showing o5% donor cells was associated with irreversible graft loss. In conclusion, early second UCBT after primary GF is a feasible treatment option. Chronic GVHD and viral reactivation are common post transplant.

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