Study compares cord blood to bone marrow for transplants

Umbilical cord blood transplants may offer blood cancer patients better outcomes than bone marrow transplants, according to an analysis of outcome data performed at the Statistical Center, Center for Blood and Marrow Transplant Research (CIBMTR), Medical College of Wisconsin, Milwaukee.

This is the first large study in children to directly compare matched bone marrow, which is currently considered the preferred graft, to matched and mismatched umbilical cord blood. There is considerable controversy in the medical community about which source of blood stem cells (cord blood or marrow) should be considered the ‘gold standard' for the treatment of childhood leukemia.

In this study, the investigators compared outcomes of pediatric leukemia patients who received unrelated bone marrow transplants versus those who received umbilical cord transplants. All bone marrow donors were matched with their recipients using very sensitive methods to determine donor and recipient tissue types.

Nearly all cord blood donors were mismatched. Up until now, no study had compared cord blood to bone marrow with this degree of HLA-matching.
The main objective of this analysis was to provide guidelines to transplant physicians on the selection of the best donor for children with leukemia.

Remarkably, mismatched cord blood performed as well as matched bone marrow as measured by leukemia free survival rates as long as the degree of mismatch was limited and the number of cord blood cells available was sufficient.

Furthermore, study participants who received matched cord blood had a 20 percent higher survival rate than matched bone marrow recipients though the number of matched cord blood transplants was small.

The research appears in this week's issue of the Lancet . Mary Eapen, M.D., M.S., Associate Professor of Pediatrics at the Medical College of Wisconsin and Associate Scientific Director of the CIBMTR is the lead author. The study was done in collaboration with the National Cord Blood Program, New York Blood Center, led by Drs. Pablo Rubinstein and Cladd Stevens. John E. Wagner, M.D., Professor of Pediatrics and Director of the University of Minnesota Division of Pediatric Hematology/Oncology and Bone Marrow Transplantation and co-chair of the CIBMTR Graft Sources Working Committee is the senior investigator.

“What this study suggests is that cord blood need not be considered as a second line therapy in children with leukemia who may benefit from a transplant,” said Eapen. The fact that the cord blood is banked and readily available with little notice is a great advantage. Leukemia patients can wait months for an appropriately matched bone marrow donor, during which time their disease might return. Further, most children should be able to find either a matched bone marrow donor or a minimally mismatched cord blood unit.

This study argues for greater investment in cord blood banking. As cell dose and HLA match are critical determinants of outcome, the researchers believe more funds are needed to expand the nation's inventory. Increasing the inventory will increase the chance of finding donors for ethnic and racial minorities currently underrepresented in volunteer marrow registries worldwide. Human Leukocyte Antigens (HLA) are a group of proteins on bone marrow cells that can provoke the immune system to respond. When doing bone marrow or cord blood transplants, doctors generally try to have the donors' and recipients' HLA types match as closely as possible.

While umbilical cord blood took longer to rebuild the blood making cells in the body, it was associated with a lower risk of graft versus host disease, a potentially lethal complication, especially when HLA types are mismatched. Rates of leukemia relapse, however, are lower with mismatched umbilical cord blood transplants.

The study was done by extensive review of clinical data from transplant centers around the country and reported to the Center for International Blood and Marrow Transplant Research and the National Cord Blood Program of the New York Blood Center. The analysis included transplant outcomes in 785 children younger than 16 who had the diagnosis of acute lymphoblastic leukemia (ALL) or acute myeloid leukemia (AML).

Funding for this research was provided by the National Cancer Institute, the National Heart, Lung, and Blood Institute and the National Institute for Allergy and Infectious Disease.