T-cell replete cord transplants give superior outcomes in high-risk and relapsed/refractory pediatric myeloid malignancy.

Stem cell transplant (SCT) outcomes in high-risk and relapsed/refractory (R/R) pediatric acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS) have been historically poor. Cord blood (CB) allows T-cell replete CB transplant (TRCB), enabling enhanced graft-versus-leukemia. We consecutively collected data from 367 patients undergoing TRCB (112 patients) or other cell source (255 patients) SCT for pediatric AML/MDS in the United Kingdom and Ireland between January 2014 and December 2021. Data were collected about the patient's demographics, disease, and its treatment; including previous transplant, measurable residual disease (MRD) status at transplant, human leukocyte antigen-match, relapse, death, graft versus host disease (GvHD), and transplant-related mortality (TRM). Univariable and multivariable analyses were undertaken. There was a higher incidence of poor prognosis features in the TRCB cohort: 51.4% patients were MRD positive at transplant, 46.4% had refractory disease, and 21.4% had relapsed after a previous SCT, compared with 26.1%, 8.6%, and 5.1%, respectively, in the comparator group. Event free survival was 64.1% within the TRCB cohort, 50% in MRD-positive patients, and 79% in MRD-negative patients. To allow for the imbalance in baseline characteristics, a multivariable analysis was performed where the TRCB cohort had significantly improved event free survival, time to relapse, and reduced chronic GvHD, with some evidence of improved overall survival. The effect appeared similar regardless of the MRD status. CB transplant without serotherapy may be the optimal transplant option for children with myeloid malignancy.