Surreal illustration of two glowing umbilical cords forming a tree of life, symbolizing advanced medical treatments.

Cord Blood Transplants: Can Two Be Better Than One for Leukemia?

Mira Elwood in Health & Wellness November 2025 • 4 min read.

"New research sheds light on how double cord blood transplants can significantly improve survival rates in children and young adults battling leukemia, especially when minimal residual disease is present."

Umbilical cord blood (UCB) transplantation has emerged as a viable alternative to traditional stem cell sources for patients with acute leukemia (AL) lacking an HLA-identical donor. The premise was simple: more hematopoietic stem cells translate to better outcomes. This led to the exploration of double-unit UCB transplants. However, initial results from prospective randomized studies painted a mixed picture, with double-unit transplants not always improving overall outcomes compared to single-unit transplants when an adequate cell dose was present.

A crucial factor in predicting the success of HSCT is the presence of minimal residual disease (MRD) before transplantation. MRD refers to the small number of cancer cells that remain in the body after treatment. Recent research suggested that in patients with positive pre-transplantation MRD, UCBT may offer a survival advantage compared to HLA-matched or HLA-mismatched unrelated donor transplantation. The question remained: Could these promising results be replicated in larger, prospective studies, and how does MRD status influence the effectiveness of single versus double-unit UCBT?

A recent study, published in Biology of Blood and Marrow Transplantation, delves into this question. Researchers analyzed data from a French prospective randomized study comparing single-unit and double-unit UCBT in children and young adults with acute leukemia. The primary goal was to determine how pre-transplantation MRD status affects leukemia relapse and survival rates in both single and double-unit UCBT settings.

Decoding the Cord Blood Transplant Study

Surreal illustration of two glowing umbilical cords forming a tree of life, symbolizing advanced medical treatments.

The study included 137 children and young adults undergoing UCBT, focusing on 115 patients with available data on MRD assessment performed just before the start of their pre-transplantation conditioning regimen. MRD positivity was defined as a level of ≥10-4, which was the case for 43 of the 115 patients. The research team then meticulously tracked survival rates, relapse risks, and disease-free survival over a three-year period.

The results indicated that while the overall three-year survival probability was 69.1%, the MRD level didn't significantly alter it. However, digging deeper revealed a crucial insight: In the MRD-positive group, patients who underwent double-UCBT experienced a significantly lower relapse risk compared to those who received single-UCBT. This translated to a higher three-year survival rate in the double-UCBT arm. What's more, this advantage was primarily observed in patients who hadn't received antithymocyte globulin (ATG) during their conditioning regimen.

The core findings from this research can be summarized as:

Double-unit UCBT may reduce relapse risk in MRD-positive patients.
The benefits of double-unit UCBT are most pronounced in patients not treated with ATG.
MRD status does not significantly impact survival rates overall.
UCBT continues to be a promising option, even when MRD is present.

Conversely, in the MRD-negative group, there was no significant difference in outcomes between single-unit and double-unit UCBT. This suggests that the double-unit strategy might be particularly beneficial in cases where the disease is more aggressive or resistant, as indicated by the presence of MRD.

The Future of Cord Blood Transplants

This study underscores the potential of UCBT as a curative strategy for children and young adults battling acute leukemia, even when MRD is present before transplantation. The findings suggest that a double-unit approach may enhance the graft-versus-leukemia effect, leading to improved survival rates, especially in MRD-positive patients who do not receive ATG as part of their conditioning regimen. As research continues to refine transplant strategies and identify optimal patient selection criteria, UCBT holds promise for transforming the landscape of leukemia treatment and improving outcomes for younger patients.

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This article is based on research published under:

DOI-LINK: 10.1016/j.bbmt.2018.10.016, Alternate LINK

Title: Single-Unit Versus Double-Unit Umbilical Cord Blood Transplantation In Children And Young Adults With Residual Leukemic Disease

Subject: Transplantation

Journal: Biology of Blood and Marrow Transplantation

Publisher: Elsevier BV

Authors: Laura Balligand, Claire Galambrun, Anne Sirvent, Clémence Roux, Cecile Pochon, Benedicte Bruno, Charlotte Jubert, Anderson Loundou, Sophie Esmiol, Ibrahim Yakoub-Agha, Edouard Forcade, Catherine Paillard, Aude Marie-Cardine, Dominique Plantaz, Virginie Gandemer, Didier Blaise, Fanny Rialland, Cecile Renard, Mylene Seux, Karine Baumstarck, Mohamad Mohty, Jean-Hugues Dalle, Gérard Michel

Published: 2019-04-01

Everything You Need To Know

What is Umbilical Cord Blood Transplantation (UCBT) and why is it considered for acute leukemia treatment?

Umbilical Cord Blood Transplantation (UCBT) is considered a viable alternative when a fully matched donor isn't available for patients with acute leukemia. The idea behind using umbilical cord blood is that more hematopoietic stem cells might lead to better results in treating the leukemia.

What does Minimal Residual Disease (MRD) mean in the context of leukemia treatment, and how does it relate to Umbilical Cord Blood Transplantation (UCBT)?

Minimal Residual Disease (MRD) refers to the small number of cancer cells that remain in the body after treatment. Recent research indicates that Umbilical Cord Blood Transplantation (UCBT) might offer a survival advantage in patients with MRD present prior to transplantation, compared to using HLA-matched or HLA-mismatched unrelated donors.

What were the main findings of the study comparing single-unit and double-unit Umbilical Cord Blood Transplantation (UCBT) in children and young adults with acute leukemia?

The study revealed that while the overall three-year survival probability was 69.1%, the Minimal Residual Disease (MRD) level didn't significantly alter it. However, patients with MRD who underwent double-unit Umbilical Cord Blood Transplantation (UCBT) experienced a significantly lower relapse risk, leading to a higher three-year survival rate. This benefit was most evident in patients who did not receive antithymocyte globulin (ATG) during their conditioning regimen.

How might double-unit Umbilical Cord Blood Transplantation (UCBT) improve survival rates in patients with Minimal Residual Disease (MRD), and what role does antithymocyte globulin (ATG) play?

The research suggests that double-unit Umbilical Cord Blood Transplantation (UCBT) may enhance the graft-versus-leukemia effect, especially in Minimal Residual Disease (MRD)-positive patients who do not receive antithymocyte globulin (ATG). This enhancement potentially leads to improved survival rates in these specific cases. It highlights the importance of tailoring treatment strategies based on patient characteristics and disease status.

What are the broader implications of this research on Umbilical Cord Blood Transplantation (UCBT) for the future of leukemia treatment in young patients?

The study highlights the potential of Umbilical Cord Blood Transplantation (UCBT) as a curative strategy for young patients with acute leukemia, even when Minimal Residual Disease (MRD) is present before transplantation. It emphasizes the importance of ongoing research to refine transplant strategies, optimize patient selection criteria, and continue improving outcomes for younger patients. This is crucial for transforming leukemia treatment and enhancing survival rates.