Each year, thousands of people diagnosed with life-threatening diseases, including blood cancers, myelodysplastic syndrome, sickle cell disease and many others, require bone marrow or stem cell transplants to give them the best chance at beating their diseases. These patients require finding a matching donor, and while some find a match from a family member, nearly 70 percent need an alternate donor to find a match.
How are donors matched with patients?
To find a match for a bone marrow or stem cell transplant, a patient and donor must have compatible human leukocyte antigens (HLA). HLA are proteins, often called markers, found on cells throughout your body that help your immune system distinguish your cells from those that do not belong to you. HLA gives your immune system the information it needs to do its job attacking cells that do not belong to you.
You have multiple HLA genes which code for the HLA proteins; half are inherited from your mother and half from your father. That is why patients in need of a donor often turn to family to find a match first.
“If a patient has full siblings, then the patient and siblings will be HLA-typed. A cheek swab can be done preliminarily to gather DNA for the HLA typing. Usually, we just use a blood test to document and confirm the match,” says David Topolsky, MD, Hematologist-Oncologist & Medical Oncologist at Cancer Treatment Centers of America® in Philadelphia, Pennsylvania. “If the patient doesn’t have a sibling, or a sibling is not a match, alternate donors may be other relatives, or we can search among unrelated donors or through the cord blood registry.”
If an unrelated donor is a match or if there is a match through a cord blood registry, the match closest to a 100% match is best. For siblings, there may be an opportunity to have less than a 100% match.
“Nowadays, we can do haplo-identical, half-match transplants for some blood cancers. In addition to the HLA genes and their proteins, there are other genes that also play a role in helping the immune system identify self-versus-non-self,” says Dr. Topolsky.
Becoming a donor
Joining a donor registry is simple, just requiring a cheek-swab or a small vial of blood as an initial test. This provides the registry with a minimum of 6 basic HLA markers to indicate if you may be a match. If you are a match at a basic level, further testing is required. About 1 in 430 members of the Be The Match Registry in the US will go on to donate marrow or stem cells to a patient.
As a donor, there are two ways you can donate to help a person get the treatment they need. Peripheral blood stem cell (PBSC) donation is used in about 75% of cases. PBSC donation is an outpatient procedure that collects blood stem cells via the bloodstream. It takes between four and eight hours on one to two consecutive days. It also requires the donor to take a medication for four to five days prior to the donation to stimulate cells for collection.
Bone marrow donation is used in about 25% of cases, most often for pediatric patient recipients. Bone marrow donation collects marrow cells from the back of your pelvic bone during a one to two-hour surgical procedure performed under anesthesia.
“While both types of donation are relatively simple, it’s important to know what to expect,” says Dr. Topolsky. “If you’re donating stem cells, you may experience some pain in preparation because of the growth factor used to stimulate stem cells. For bone marrow donation, you may experience some pain after the surgical procedure when anesthesia wears off.”
Many people wonder if they qualify to be a donor. If you are between the ages of 18 and 60, you can register to donate through Be The Match®, the National Marrow Donor Program, as long as you meet some health guidelines. In fact, many cancer survivors can register to donate depending on their cancer type, the extent of their disease and if they had chemotherapy and/or radiation as part of their treatment.
“If you have a sibling who needs a transplant, their transplant team will determine if you can donate to them,” says Dr. Topolsky. “If you’re not a match, or your health history precludes you from donating, their team will search the registry to find a match.”