In patients with acute leukemia, detection of minimal residual disease (MRD) before allogeneic hematopoietic cell transplantation (HCT) correlates with risk of relapse. However, the level of MRD that is most likely to preclude cure by HCT is unclear, and the benefit of further chemotherapy to reduce MRD before HCT is unknown. In 122 children with very-high-risk acute lymphoblastic leukemia (ALL; n = 64) or acute myeloid leukemia (AML, n = 58), higher MRD levels at the time of HCT predicted a poorer survival after HCT (P = .0019); MRD was an independent prognostic factor in a multivariate analysis (P = .0035). However, the increase in risk of death associated with a similar increment of MRD was greater in ALL than in AML, suggesting that a pretransplantation reduction of leukemia burden would have a higher impact in ALL. At any given MRD level, survival rates were higher for patients treated in recent protocols: the 5-year overall survival for patients with ALL was 49% if MRD was detectable and 88% if it was not and the corresponding rates for patients with AML were 67% and 80%, respectively. Although MRD before HCT is a strong prognostic factor, its impact has diminished and should not be regarded as a contraindication for HCT.

We evaluated 190 children with very highrisk leukemia, who underwent allogeneic hematopoietic cell transplantation in 2 sequential treatment eras, to determine whether those treated with contemporary protocols had a high risk of relapse or toxic death, and whether non-HLA-identical transplantations yielded poor outcomes. For the recent cohorts, the 5-year overall survival rates were 65% for the 37 patients with acute lymphoblastic leukemia and 74% for the 46 with acute myeloid leukemia; these rates compared favorably with those of earlier cohorts (28%, n ‫؍‬ 57; and 34%, n ‫؍‬ 50, respectively). Improvement in the recent cohorts was observed regardless of donor type (sibling, 70% vs 24%; unrelated, 61% vs 37%; and haploidentical, 88% vs 19%), attributable to less infection (hazard ratio [HR] ‫؍‬ 0.12; P ‫؍‬ .005), regimen-related toxicity (HR ‫؍‬ 0.25; P ‫؍‬ .002), and leukemiarelated death (HR ‫؍‬ 0.40; P ‫؍‬ .01). Survival probability was dependent on leukemia status (first remission vs more advanced disease; HR ‫؍‬ 0.63; P ‫؍‬ .03) or minimal residual disease (positive vs negative; HR ‫؍‬ 2.10; P ‫؍‬ .01) at the time of transplantation. We concluded that transplantation has improved over time and should be considered for all children with very high-risk leukemia, regardless of matched donor availability. (Blood. 2011;118(2):223-230)

HLA-matched related donor (MRD) hematopoietic stem cell transplantation (HSCT) is a well-established therapy for patients with sickle cell disease (SCD); however, experience using alternative donors, including haploidentical donors, in HSCT for SCD is limited. We report the long-term outcomes of 22 pediatric patients who underwent related donor HSCT for SCD at St. Jude Children’s Research Hospital, either a myeloablative sibling MRD HSCT (n = 14) or reduced-intensity parental haploidentical donor HSCT (n = 8). The median patient age was 11.0 ± 3.9 years in the MRD graft recipients and 9.0 ± 5.0 years in the haploidentical donor graft recipients. The median follow-up was 9.0 ± 2.3 years, with an overall survival (OS) of 93% and a recurrence/graft failure rate of 0%, for the MRD cohort and 7.4 ± 2.4 years, with an OS of 75%, disease-free survival of 38%, and disease recurrence of 38%, for the haploidentical donor cohort. We report the long-term hematologic response and organ function in patients undergoing MRD or haploidentical donor HSCT for severe SCD. Our data demonstrate long-term hematologic improvements after HSCT with sustained engraftment, and confirm that HSCT offers long-term protection from common complications of SCD, including stroke, pulmonary hypertension, acute chest, and nephropathy, regardless of donor source.