John WagnerUniversity of Minnesota-led study, published in June 9, 2007 issue of the journal Lancet, has shown that children with Leukemia did just as well with umbilical cord blood transplant as with bone marrow transplant. The best part of the news is that the cord blood didn’t have to be matched to the recipient; as long as the degree of mismatch was limited and the number of cord blood cells available was sufficient.

In the study patients receiving cord blood had the same five-year leukemia-free survival rates as those who received bone marrow.

This will tremendously help in providing a ready supply of white blood cells to leukemia patients from ethnic and racial minorities, who now have great difficulty finding a donor because they are underrepresented in volunteer marrow registries worldwide. Now we can find donors for majority of patients.

Cord blood transplant proved to be even more amazing. In traditional bone marrow transplant doctors match eight HLA antigens to reduce the chance of rejection later and to minimize the change of almost always fatal graft versus host disease. This significantly limits the pool of donors for bone marrow transplant recipients. The “gold standard” of matching is where all the antigens match. Diversity of HLA in human population is one aspect of disease defense, and, as a result, the chance of two unrelated individuals having identical HLA molecules on all loci is very low.

Note: The human leukocyte antigen system (HLA) is the name of the human major histocompatibility complex (MHC). This group of genes resides on chromosome 6, and encodes cell-surface antigen-presenting proteins and many other genes.

In this study the researchers compared 503 cord blood recipients from around the country (USA) with various degrees of mismatching to 282 “gold standard” matched bone marrow recipients, looking for difference in the five-year survival rate. The results were surprising to say the least.

In cord blood, “with every increment in mismatch, we found a correspondingly increased anti-leukemia effect. That means the risk of relapse of leukemia became substantially lower with every level of mismatch.” Although it seems counterintuitive, such an effect is also known to occur with bone marrow transplants, but the study found it to be even stronger with cord blood. In other words, even with mismatched cord blood, overall five-year survival rates were comparable to the gold standard of bone marrow transplants, says senior investigator John Wagner, a University of Minnesota professor of pediatrics and director of the division of pediatric hematology/oncology and bone marrow transplantation.

In both cases, the rate was about thirty-eight percent. Umbilical cord blood also was associated with a lower risk of graft versus host disease.

So to summarize:
1. Mismatch of cord blood actually enhanced anti-leukemia effect. This pretty much opens wide the donor pool
2. Umbilical cord blood transplants are associated with lower graft versus host disease
3. Higher numbers of cells in cord blood transplants improved survival rates.

However, says Wagner, increasing levels of mismatch in cord blood transplants were associated with higher risks of death from transplant-related complications, most commonly infection. This, speaking from experience, is manageable if you are careful.

It takes an average of two to four months to obtain marrow from adult volunteer donors. In contrast, cord blood units are already sitting in a bank and can be used once a confirmatory typing for matching purposes is completed, which takes a week or two. It is crucial, says Wagner, to increase the diversity in cord blood banks. via Insight News []

This study brings forward cord blood transplant as a primary form of therapy for leukemia as opposed to its previous status as secondary line of therapy, where bone marrow transplantation was unavailable. This will give more flexibility of timing the transplant to leukemia patients needs and not have them dependent solely on availablity.