While 6.8 million people identified themselves as multiracial in the 2000 census, only a tiny fraction of them are among the millions of registered bone marrow donors. For that reason, a Caucasian lymphoma patient who needs a bone marrow transplant has almost a 90 percent chance of finding a genetically-compatible donor, while multiracial patients have little to no chance.
I spoke recently about this problem with Dr. Laurence Cooper, associate professor of pediatrics at the Children's Cancer Hospital at The University of Texas MD Anderson Cancer Center, which performs more bone marrow transplants than any other institution in the nation.
Explain what bone marrow transplantation is and why we use it.
Bone marrow transplantation is a procedure that's been around for decades now. It has a track record for typically helping patients who have cancer diagnoses. We often do transplants that no longer involve bone marrow, but involve other sources of hematopoietic [blood-derived] stem cells. This transplantation provides the recipient the opportunity to reset their immune system. Patients typically get conditioning therapy to prepare them for the transplantation. This can be chemotherapy or radiation. That allows them to receive the graft from their donor. Then, they're in a state where they're heavily immuno-suppressed. They will not reject the incoming cells. The graft from the donor is infused. That graft starts making elements in the blood stream, such as white blood cells, for the purpose of reconstituting that recipient's blood stream and, in particular, to give back elements of the immune system. It's those elements of the immune system that are really critical in providing that biologic effect. For instance, T-cells from the donor bubble out of the bone marrow and can patrol the body looking for remaining tumor cells. The can go after the tumor cells and kill them and then that patient can enjoy long-term remission.
Talk about the problem you're facing with bone marrow for multiracial patients.
The first choice of donor is within the family. Any particular patient has about a one-in-four chance that their sibling is going to be an HLA [human leukocyte antigen] match. This concept of HLA, these molecules that allow an immune system to be recognized, is really one of the central elements of transplant biology. When you're born, from your parents you get sets of chromosomes. On the chromosomes, you have genes that code for the pattern of HLA molecules that you have for the rest of your life. If you think about a patient undergoing transplant, what we're trying to do is essentially to reset their immune system. We're trying to give that person a new set of immune cells, for instance of T-cells, which will recognize their tumor. We want to be able to do that so the T-cells will recognize the HLA on the tumor.
Once you start going outside the family, it becomes more difficult to identify those patients that have those same HLA. The chances of one person being a match for another person are very unusual. The way to answer this problem has been that people have been willing to give up their time and a little bit of their blood and they go on these huge [donor] registries. By searching these large computer registries, we can find a needle amongst the haystack. If you're white, we tended to be in the registries disproportionately to other groups. If you belong to a racial minority, you may [be part of] a small pocket of people and they may not have participated in the huge, global registries. When you get into issues now where sub-groups of particular minorities are searching the registry, it can become quite frustrating. It can be difficult to find a match.
How can this problem be fixed?
For these patients who are challenged in finding a donor, there's a three-pronged answer.
- We want people to donate who are from minority groups and who have mixed parenting. They are a special pool and could give to other people who are like themselves. If you could get more potential donors out there, you could essentially enjoy the same benefits as Caucasians.
- The second answer is we want people to donate their cord blood. If more people donate their cord blood, the chances of us finding a near-miss go up. It doesn't have to be perfect. We can find a nearly HLA identical child who has given up his or her cord blood at the time of birth.
- We continue to develop new technology to overcome [these] issues where we can develop transplants for special groups [using] donors that are HLA mismatched, but [we can] do special maneuvers.
How to register as a donor:
Image: Dr. Laurence Cooper
This post was originally published on Smartplanet.com