Allogenic Stem Cell Transplants

In the most common type of allogeneic transplant, the stem cells come from a donor whose tissue type closely matches the patient’s. (This is discussed later under “HLA matching” in the section called “ Donor matching for allogeneic transplant.”) The best donor is a close family member, usually a brother or sister. If you do not have a good match in your family, a donor might be found in the general public through a national registry. This is sometimes called aMUD (matched unrelated donor) transplant. Transplants with a MUD are usually riskier than those with a relative who is a good match. Blood taken from the placenta and umbilical cord of newborns is a newer source of stem cells for allogeneic transplant. Called cord blood, this small volume of blood has a high number of stem cells that tend to multiply quickly. But the number of stem cells in a unit of cord blood is often too low for large adults, so this source of stem cells is limited to small adults and children. Doctors are now looking at different ways to use cord blood for transplant in larger adults, such as using cord blood from 2 donors.
Pros of allogeneic stem cell transplant: The donor stem cells make their own immune cells, which could help destroy any cancer cells that remain after high-dose treatment. This is called the graft-versus-cancer effect. Other advantages are that the donor can often be asked to donate more stem cells or even white blood cells if needed, and stem cells from healthy donors are free of cancer    Cons to allogeneic stem cell transplants: The transplant, also known as the graft, might not take — that is, the donor cells could die or be destroyed by the patient’s body before settling in the bone marrow. Another risk is that the immune cells from the donor may not just attack the cancer cells – they could attack healthy cells in the patient’s body. This is called graft-versus-host disease. There is also a very small risk of certain infections from the donor cells, even though donors are tested before they donate. A higher risk comes from infections you have had, and which your immune system has under control. These infections often surface after allogeneic transplant because your immune system is held in check (suppressed) by medicines called immunosuppressive drugs. These infections can cause serious problems and even death. Allogeneic transplant is most often used to treat certain types of leukemia, lymphomas, multiple myeloma, myelodysplastic syndrome, and other bone marrow disorders such as aplastic anemia.