When a transplant is needed, there are three possible sources. Bone marrow, peripheral blood stem cells (PBSCs) and cord blood. The ideal situation is that a patient has a familial match from either the bone marrow or PBSCs of a relative. Matches are genetically based. The human leukocyte antigen, or HLA, type genes coded into each person’s unique genetic background are the lynch pin to a successful transplant. It is the similarity between the donor HLA genes and the recipients genes that determines the odds of the donor stem cells being rejected or accepted. Typically a 10-out of-10 match of HLA genes between patients and their donors is the gold standard, but it doesn’t happen that often. Without that kind of match, a transplant can be done with an 8 out of 10 match or a 9 out of 10 and while these are better than nothing, for patients at a high risk for relapse the odds of success are low.
The benefit of using cord blood is that unlike adult stem cells, cord blood cells are not fully developed and a high genetic match is not as crucial as it is when using adult donor cells. Cord blood cells can match many more recipients. Since some genes are tied to ethnic backgrounds it’s not unheard of for two unrelated people, donor and recipient, being a match based on ethnicity rather than HLA genes.
In addition to the high stakes of a genetic match, there are those patients who are at an even higher risk of relapse. Chemotherapy, while required in these cases before a transplant can be done, does not always wipe out all of the disease. The prognosis for this group of high risk patients who have what is called “minimal residual disease” is usually pretty poor, with less than 1/3 of them remaining alive three years after treatment. The recent study suggests cord blood transplants could be a better decision for this risk category.
In the study Drs. Fillilpo Milano and Colleen Delaney looked at the outcomes of 582 patients who received stem cell transplants from 2006, when the institute’s Cord Blood Program launched, to 2014. Of those, 140 patients received cord blood transplants. The results revealed that the probability of overall survival after receipt of a transplant from a cord-blood donor was at least as high as those patients who got a transplant from an HLA-matched unrelated donor. When comparing patients who received cells from an HLA-mismatched unrelated donor, the cord blood recipients had a higher survival rate. Relapse rates were lower in the cord blood group as well.
In a press release about the study, Dr. Delaney stated, “This brings home the point that cord blood shouldn’t be called an alternative donor. The outcomes are the same as a conventional donor. This paper shows that if you’ve got high-risk disease and are at high risk for relapse post-transplant, transplant with a cord blood donor may be the best option.” Learn more about this new information in the video below.
Sources: Fred Hutchinson Cancer Center, New England Journal of Medicine
National Marrow Donor Program