For the purpose of transplant, donor stem cells are collected in two ways:
- Bone Marrow Harvest
Bone marrow from the back of both the hip bones is removed. The amount of marrow retrieved depends on upon the weight of the receiver.
The donor is given shots for several days to help the stem cells move from the bone marrow to the blood. The white blood cells containing the stem cells are then separated with the support of a machine and are later given to the recipient. The red blood cells are then returned to the donor.
Types of Transplant
There are various methods of transplantation. Choosing to undergo which type is complicated and needs to be discussed with the surgeon who specializes in transplant. The following explains the type of stem cell transplant procedures that are available.
- Autologous Transplant / AUTO Transplant
In this kind of transplantation, a patient gets his own stem cells after the doctors have treated cancer.The stem cells are first collected from the blood by the health care team and frozen. Next, the patient undergoes powerful chemotherapy and sometimes even radiation. The frozen stem cells are then thawed and put back in the blood through a tube which is placed in the vein (IV) and known as the central venous catheter. In about 24 hours the stem cell reaches the bone marrow, start to grow, then multiply and help the marrow in making healthy blood cells once again. This type of transplantation is possible only if the patient has a healthy bone marrow.
- Syngeneic Transplant
In this type of bone marrow transplantation, the patient receives marrow which is donated by his / her healthy identical twin. The method provides the simplest source of stem cells and is the least complicated of transplants as there is no risk of rejection, GVHD or tumor in the marrow. The blood cell recovery is also fast the immune system returns to functioning promptly.
- Allogeneic Transplant / ALLO Transplant
In this type of stem cell transplant, the patient gets stem cells from a donor whose bone marrow has to match that of the patient. This transplant is carried out when the bone marrow cells are damaged. Since the donor has to be a close genetic match, the best donor choice is a compatible relative, although genetic matches are also available from other donors. Proteins are known as Human Leukocyte Antigens (HLA) which are present in the white blood cells should match as closely as is possible in both the donor and the recipient; else there is a possibility of graft-versus-host-disease (GVHD).
Once a donor match is found, the patient undergoes chemotherapy which may or may not be accompanied by radiation. The donor stem cells are then given to the patient through the central venous catheter. Since the stem cells in this type of transplantation are not frozen, they can be given soon after the chemotherapy or radiation therapy is over.
- Umbilical Cord Blood Transplant
In case a donor match is not available this option can be used where the cord blood is used. This is also a type of allogeneic transplantation where stem cells from the umbilical cord of a newborn baby are removed right after birth. These stem cells are frozen and stored to be used later in transplantation. There is less need for matching since the blood cells of the umbilical cord are very immature.Since the stem cells are in smaller number, the recovery time for blood counts is much longer in umbilical cord blood transplant.