There are three kinds of blood and marrow transplant: autologous, allogeneic, and syngeneic. The types indicate where, or who, the stem cells come from.
What is an autologous transplant?
In an autologous transplant, you receive your own stem cells. The cells are harvested from your body after you undergo salvage chemotherapy or induction chemotherapy. The cells are then frozen and stored while you receive a conditioning regimen of chemotherapy and/or radiation in order to eliminate the remaining cancerous cells in your body.
After the conditioning regimen, your stem cells are returned to you through an infusion. In the absence of cancerous cells, they should be able to begin producing healthy blood cells in the bone marrow.
If you receive an autologous transplant, your cancer is actually cured by the chemotherapy – the reintroduction of the stem cells just resuscitates the bone marrow, which is destroyed by the strong doses of chemo.
What is an allogeneic transplant?
In an allogeneic transplant, stem cells are contributed by a donor. The cancer is cured, not by the chemotherapy or radiation, but by the donor’s immune system. The donor’s stem cells must be a “match” for your own. Doctors look at genes called human leukocyte antigens to determine whether a donor will be a good match or not. There are several options for finding donated stem cells.
- A relative: Close blood relatives, such as your parents, siblings, or children, are more likely to have similar antigens to you. There’s an approximately 25 percent chance that one of your relatives will be a complete match.
- An unrelated donor from a registry: If none of your family members match, or you don’t have enough living family members to test, we will look for a donor for you on the National Marrow Donor Program Registry (NMDPR). The NMDPR connects patients with donors from across the country, and sometimes from around the world.
- Cord blood: Sometimes, a match will be found through an umbilical cord blood bank. This type of transplant is more common in pediatric patients.
What is a syngeneic transplant?
If you have an identical twin, he or she may be able to donate stem cells for you in what’s termed a syngeneic transplant. The process works just like an allogeneic transplant, except the donor is guaranteed to be a perfect match.
What if I can't find a donor?
If there is difficulty locating a donor who matches your human leukocyte antigen profile, it is still possible to receive a transplant using cells from one of your close relatives, even if he or she is not a complete match. This is a type of allogeneic transplant called a haploidentical or half-match transplant. Washington University Physicians at Siteman Cancer Center have been performing an increasing number of half-match transplants in recent years, with positive results.