Autologous stem cell transplant: This kind of transplant is mainly used to treat lymphomas and multiple myeloma, although it is sometimes used for other cancers. In this type of transplant, you are your own donor, using stem cells from either your bone marrow or circulating blood. Your stem cells are removed before treatment through a process called harvesting, and then frozen. After you have received high doses of chemotherapy, radiation, or both, the stem cells are thawed and given back to you.

An advantage of autologous stem cell transplant is that you are getting your own cells back, so there is no risk that your immune system will reject the transplant or that the transplanted cells will attack your own body.

A possible disadvantage is that cancer cells may be harvested along with the stem cells and then reinfused back into the body. Doctors sometimes treat the cells first with anticancer drugs or other therapies to reduce the number of cancerous cells that may be present. This is called purging.

Allogeneic stem cell transplant: This type of transplant is commonly used to treat leukemias and other bone marrow disorders. Here, the stem cells come not from the patient, but from a donor whose tissue type best matches the patient. The donor is most often a family member, usually a brother or sister, but if you do not have a good match in the family, one can often be found from the general public through a national registry. A newer source of stem cells is blood taken from the placenta and umbilical cord of newborns. This blood contains a relatively high number of stem cells. Still, the numbers are often too low for adults, so this source of stem cells is used mostly in children.

An advantage of allogeneic stem cell transplant is that the donor stem cells produce their own immune cells, which may help destroy any cancer cells that remain after high-dose treatment. Another possible advantage is that the donor can often be recalled if needed to donate more stem cells. Stem cells from healthy donors are also free of cancer cells.

But there are several possible drawbacks to allogeneic stem cell transplant as well. The transplant, also known as a graft, may not "take" – that is, the donor cells may be more likely to die or be destroyed by the patient’s immune system before settling in the bone marrow. Another possibility is that the donor cells will create new immune cells that attack the recipient’s body – a condition known as graft-versus-host disease. There is also a very small risk of certain infections from the donor cells (although donors are always tested beforehand to minimize this risk).

Syngeneic stem cell transplant: This is a special kind of allogeneic transplant because the donor is an identical twin with identical tissue types. Since few people are identical twins, this type of transplant is very rare. An advantage of syngeneic stem cell transplant is that graft-versus-host disease is not a problem. A disadvantage is that this type of transplant won’t help destroy the cancer cells.

Revised 09/04