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Bone Marrow/Stem Cell Transplant Frequently Asked Questions
4. How are the stem cells used in transplant collected?
The stem cells used in transplant are collected from one of three sources:
Stem cells are collected from the patient's or donor's bone marrow. Historically, this was the way that all stem cells were collected for transplantation, hence the common usage of the term "bone marrow transplantation." The bone marrow collection is performed under general or spinal anesthesia. As such, the donor or patient doesn't feel significant pain or discomfort during the marrow collection. This is an outpatient procedure, and the donor (or patient, in the case of an autologous transplant) usually goes home the same day. However, some soreness can be expected in the lower back after the procedure for a few days or longer. This discomfort can be well-controlled with oral pain medication.
The doctors use large, hollow needles to withdraw the liquid marrow from the back of the pelvic bone. The hip bones in the pelvis are used as a collection site because in the adult they are marrow-rich and contain the stem cells.
When the collection is complete, the donor or patient will be given instructions about icing, a prescription for pain medication if needed, and other recommendations for care. The amount of marrow taken in each case varies depending on the size of the transplant recipient. More marrow is needed for a large adult compared to a child.
In general, the amount of marrow removed from the donor's body will replenish itself within four to six weeks. In some cases, marrow donors will have a unit of their red blood cells collected in advance for transfusion during or after the harvest procedure. This would minimize the anemia (from blood loss) that may occur after the procedure. Don't hesitate to discuss any of these procedures with the BMT physician or nurse coordinator prior to donation.
When stem cells are collected from the circulating blood, the procedure is more like a blood or platelet donation. The stem cells in the circulating blood are called peripheral blood stem cells (PBSC). Like the stem cells in the bone marrow, they are able to divide and produce red cells, white cells, and platelets.
The concentration of peripheral blood stem cells in the blood, however, is very low under normal circumstances. So before collecting the cells, medications (called colonystimulating factors or growth factors) are given to the donor to stimulate the bone marrow to produce more stem cells, which are then released into the blood stream. Most growth factors are administered as injections under the skin for approximately five days. The duration of growth factor administration and the number of collection procedures will depend on the number of stem cells collected. Ask the collection center staff for guidance. The donor should not stop taking the growth factor unless advised. It is important that the correct dose of growth factor be administered around the same time each day. Physicians should be contacted immediately if any side effects occur.
Once these stem cells are released into the blood, they are collected in one or more sessions. During this procedure, blood is removed through a needle in the donor's vein. Each session normally takes four to six hours. Stem cell collections are performed as outpatient procedures. Donors should plan to spend most of the day at the collection center on the day of collection. In this procedure, called apheresis, the blood circulates through a machine called a cell separator that removes the peripheral blood stem cells and returns the rest of the blood to the body.
For autologous bone marrow transplants, the stem cells are then stored and frozen until the time of the transplant. In an allogeneic transplant, stem cells are commonly infused fresh. However, in some circumstances, the cells from a related donor are frozen and stored prior to infusion.
Since the first cord blood transplant in 1988, tremendous strides have been made in this field. Umbilical cord blood can be donated by parents when a child is born. Umbilical cord blood is rich in stem cells, and an increasing number of hospitals have the ability to collect the blood from the umbilical cord using special kits.
Cord blood plays an important role in transplant today. The use of cord blood transplants has increased for both children and adults. Cord blood is used more often in children because a cord blood unit has a limited amount of blood-forming cells. Smaller patients need fewer cells, and larger patients may need two cord blood units combined.
Because cord blood cells are less immunologically mature compared to cells collected from adult donors, they can be used for transplantation even when there is a greater degree of human leukocyte antigen (HLA) mismatching between the patient and the cord blood unit. A close HLA match reduces the risk that your immune cells will attack the donor's cells or that the donor's cells will attack your body. As such, cord blood may offer a chance for transplant for patients who otherwise do not have any suitably matched adult donors.
There are potential advantages and disadvantages of using cord blood for a transplant. In some studies, patients who receive a cord blood transplant experienced less severe GVHD. However, a cord blood transplant may also carry a higher risk of graft failure, slower blood count recovery, and infection. As always, it is important to discuss the benefits and risks of a cord blood transplant with your doctor.
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