Unrelated Donor Bone Marrow Transplants in Children

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Abstract
Only a small proportion of children who might benefit from bone marrow transplant (BMT) have an HLA-identical sibling. To provide this potentially curative therapy to patients without a matched related donor, marrow transplants using less well matched related donors or unrelated donors (identified through computerized donor registries) have been performed. We report the outcome of 24 consecutive unrelated donor BMT's performed on children. Eligible diagnosis included acute leukemia (AL) (n = 15), chronic myelogenous leukemia (CML) (n = 4), myelodysplastic syndrome (MDS) (n = 3), and severe aplastic anemia (SAA) (n = 2). All donor/recipient pairs were sero-matched at 5 or 6 of the 6 HLA A, B, and DR antigens. Several different preparative regimens were used, but fractionated total body irradiation (TBI) was used in 20 patients. All recipients received graft-versus-host-disease (GVHD) prophylaxis with cyclosporine-A (CSA), four with short course methotrexate (MTX), 14 in combination with short course MTX and methylprednisolone (MPS), and five in combination with a mouse monoclonal antibody to CD5, coupled to the A-chain of ricin (Xomazyme-65). One patient received CSA and MPS alone after a T-cell depleted marrow transplant. Twenty of 23 evaluable recipients engrafted (87%). Two patients with CML never engrafted and had autologous marrow recovery, one patient with SAA died at 128 days without evidence of engraftment, and there was one early death at day + 9. Fourteen of 20 patients (70%) with stable donor-derived hematopoiesis developed significant acute GVHD ≥ grade II). Eleven of 15 engrafted patients who survived > 100 days after BMT developed chronic GVHD (73%). Thirteen patients survive, 10 disease-free; 2 yr actuarial survival and disease-free survival are 47% and 41%, respectively. Of the 19 engrafted patients with leukemia or MDS, only three have relapsed. The actuarial relapse risk at 2 yr is 24%. Unrelated donor transplants in children are associated with an increased risk of GVHD and nonengraftment compared to matched sibling transplants. Increased donor age is significantly associated with a greater risk of acute GVHD.