Stem Cell Transplantation

Overview :

Stem cell transplants sometimes are called bone marrow transplants. Nearly 100 years ago, physicians tried to give patients with leukemia and anemia bone marrow by mouth. These treatments were not successful, but led to experiments showing healthy bone marrow transfused into the blood stream could restore damaged bone marrow.

Today, two types of stem cell transplants are performed most often. When a patient's own stem cells are collected (harvested) before they are destroyed by high-dose chemotherapy or radiation therapy treatments, then returned to the same patient's body, it is called an autologous transplant. Using stem cells from another person, or a donor, is called allogenic transplant. In many cases, donor cells come from a relative, such as a brother or sister. However, the likelihood that a sibling will match the patient is only about 25%. Stem cells may need to come from a person not related to the recipient.

To find out if a patient could receive stem cells from a donor, physicians developed human leukocyte antigen (HLA) testing to match tissue types. The next challenge became finding donors. Throughout the 1980s and 1990s, private individuals, hospitals, foundations, and states worked to set up a nationwide registry of bone marrow donors. The National Marrow Donor Program (NMDP) now has the largest stem cell donor registry in the world. In July 2003, more than five million volunteer donors and more than 28,000 units of umbilical cord blood were listed on the NMDP registry. More than 16,000 bone marrow transplants have been performed since the NMDP was founded in 1986.

Stem cell transplants normally take place at specialized centers. Donor cells are taken from the donor in an operating room while the patient is unconscious and under general anesthesia. Bone marrow normally is harvested from the top of the hip bone. The marrow usually is filtered, treated, and either transplanted immediately or frozen for later use. Stem cells are transfused through an intravenous (IV) catheter that physicians insert in the patient's neck or chest. Physicians refer to this step as the "rescue process." The stem cells replace old cells. For example, the transplanted cells travel to the bone cavities and begin replacing old bone marrow.