Stem cell transplantation

[Luis Fok]

Stem cell transplantation is the removal of stem cells (undifferentiated cells) from a healthy person and their injection into someone who has a serious blood disorder.
(See also Overview of Transplantation.)
Stem cells are unspecialized cells from which other more specialized cells can be derived. Stem cells may be obtained from

Blood in the umbilical cord of a baby after it is born (donated by the mother)
Bone marrow (bone marrow transplantation)
Blood

Blood is preferred to bone marrow as a source because the procedure is less invasive and the number (count) of blood cells returns to normal more quickly. Stem cells from umbilical cords are usually used only in children because umbilical cord blood does not contain enough stem cells to use in adults.
Stem cell transplantation can be used as part of the treatment for blood disorders such as leukemia, certain types of lymphoma (including Hodgkin lymphoma), aplastic anemia, thalassemia, sickle cell disease, and some congenital metabolic or immunodeficiency disorders (such as chronic granulomatous disease).
Stem cell transplants may also be given to people who have been treated with high doses of chemotherapy or radiation therapy for certain cancers. Such treatments destroy bone marrow, which produces stem cells. Occasionally, stem cell transplants can be used to replace bone marrow cells that are destroyed during treatment of cancers in organs, such as breast cancer or neuroblastoma (a common childhood cancer that develops from nerve tissue). Doctors are studying how to use stem cell transplantation to treat some autoimmune disorders, such as multiple sclerosis.
About 30 to 40% of people who had lymphoma and 20 to 50% of those who had leukemia are cancer-free after treatments, including stem cell transplantation. The procedure prolongs life in people with multiple myeloma. It is less effective for breast cancer.