If you need an allogeneic (donor-provided) stem cell transplant, MSK can help. We can find you a stem cell donor whether you have a donor who is fully matched or not.
How are stem cell donors matched to you?
People are matched with possible stem cell donors using human leukocyte (LOO-koh-site) antigen (HLA) genes. HLA genes control how the immune system works and how it knows tissue is not yours.
There are 4 different HLA genes. Together they make a set called a haplotype. Everyone has 2 HLA haplotypes, one set from each parent. This makes a total of 8 HLA “markers.”
How do people who need a stem cell transplant find a matched donor?
There are 2 ways people find a stem cell donor. A family member can be a donor or someone unrelated to you can be found through a donor registry. Unrelated means they’re not someone in your family related to you by blood.
Family member donor matches
Siblings (brothers or sisters) who have the same mother and father may share both HLA haplotypes, or 1, or none. They can be:
- A complete match
- Half matched (also called haploidentical)
- Not matched at all
Siblings from the same mother and father have a 1 in 4 chance of being completely matched and a 1 in 2 chance of being half-matched (haploidentical).
Some family members have health issues that mean they will not be a good donor. Younger donors are sometimes preferred. For these reasons, even if you have a brother or sister who is a full match, they may not be the best donor.
Unrelated donors from a registry
The HLA markers inherited (passed on) from your parents can also match people who are unrelated to you. Donor registries have been set up to make matches between patients and donors who are not related to each other.
There are now more than 40 million donors in registries around the world. MSK will do a very thorough search among registries in the United States, such as NMDP, and also ones in other countries, if necessary.
Why is it harder for some people to find a fully matched donor?
A “matched” donor is generally considered to be matched among 8 key HLA genes. Sometimes these donors are called “8/8” matched. Many people who need a transplant cannot find a fully matched donor in any registry.
Finding a donor is a real challenge for people from some racial and ethnic backgrounds. This includes southern European, Asian, African, Hispanic, Middle Eastern, or mixed ethnic backgrounds.
People with these ethnic backgrounds often have tissue types that are less common in donor registries. This can make it hard or impossible for some people to find a fully matched donor from a registry.
Do you need a fully matched stem cell donor for transplant?
You do not need a fully matched donor to have a successful stem cell transplant. At MSK, people with a partial-match stem cell transplant have outcomes similar to people who undergo a transplant with a fully matched donor.
At MSK, transplant planning starts with thorough research on available family and unrelated donors. We’ll work with you to find the best donor. Donors may be fully matched, half matched, or partially matched (also called mismatched).
MSK’s goal is to find a stem cell donor who is available soon. We try to avoid delays in giving you the transplant.
MSK is a leader in using HLA-mismatched, unrelated stem cell donors.
MSK has deep experience in the best methods for selecting the right donor. We make sure HLA-mismatched blood stem cells will grow well after they’re transplanted.
We’re also a leader in finding new ways to stop the immune system from rejecting donor stem cells. That’s a common issue for people with half matches or partial matches.
Our research shows people who have a stem cell transplant from a mismatched donor do very well. They have similar results, including a good quality of life, compared to people who get transplants from fully matched donors.
What are the options for people who do not have a fully matched stem cell donor?
MSK has a lot of experience in assessing family members and unrelated donors. We’ll work with you during the process of picking the best donor for your transplant. MSK has a few options for people who do not have a fully matched donor.
Half-matched (haploidentical) transplant
One option is to use a donor who is a half match (haploidentical). Parents and children are always haploidentical to each other, but they may not be the right age to donate.
Other haploidentical matches can be a sibling or another relative related to you by blood. This includes a niece, nephew, cousin, or grandchild.
Mismatched transplant
Unrelated donors can be matched using only some of the 8 HLA markers. These are called mismatched unrelated donors.
MSK has one of the world’s most active and successful transplant programs focused on using mismatched donors. Many of the patients that undergo transplants at MSK receive a donation that is matched at 5, 6, or 7 out of 8 key HLA markers. In fact, nearly half of our unrelated donor transplants come from donors who are not fully matched to the patient.
Cord blood transplant
MSK also offers cord blood transplants, another option for people without a fully matched stem cell donor.
Cord blood is collected from the umbilical cord and placenta of healthy newborns. It’s donated by the baby’s parents at birth. Cord blood is rich in stem cells that form blood. Cord blood is stored frozen in banks, so it may be available sooner than stem cells collected from adult donors.
Stem cell transplant clinical trials and new advances
MSK has new ways of improving the care of people who get transplants from donors who are not fully matched.
We have developed safer ways to do these transplants. Our results are some of the best in the world. We have cured many people of blood and bone marrow cancers, thanks to these types of transplants.
Our stem cell transplant clinical trials are now researching ways to speed the recovery of blood cells after a transplant. We’re also looking at how to prevent problems from transplants. Some common problems after transplants are:
- Return or relapse of the cancer
- Infections
- Graft-versus-host disease (GVHD) — when the donor’s blood cells attacks your healthy tissues