What are the different types of transplants available?
When patients give their own stem cells back to themselves, the procedure is called an autologous stem cell transplant. How can a sick person be his/her own donor and then get healthy again? It helps to think of this kind of transplant as a rescue. You may even hear your health care team refer to your transplant as a rescue. The autologous transplant isn’t necessarily performed because there’s something wrong with the bone marrow or stem cell production. It’s performed because the dosage of chemotherapy and radiation needed to kill the disease is so high that it will destroy the patient’s existing bone marrow. Without the stem cells in the marrow, there is no blood cell production or immune system, and life is not sustainable. The patient’s own stem cells, collected prior to the chemotherapy/radiation, are reinfused, like a blood transfusion, and blood cell production and the immune system are re-established. Generally, patients not achieving remission are not suitable candidates to donate stem cells for themselves. Oddly enough, however, cancers that originate in the bone marrow, such as certain types of leukemia, are sometimes treated with autologous stem cell transplants, particularly if it is not possible to use the stem cells of a donor.
Since the marrow is where the cancer originates, it is difficult to obtain totally unaffected stem cells. Even when the patient is in remission, it’s possible for some cancer cells to remain in the body. In order to deal with this, many transplant centers have developed methods of purging or cleansing the stem cell
product and ridding it of most of the cancerous cells. The goal is to keep the diseased cells in such a small number that the body’s defense system will be able to destroy them. Purging is done differently from center to center. Some centers, in fact, don’t do it at all. If you have questions about these issues, ask them. Your doctor and other medical professionals should be able to get you the information that you need.
Related and unrelated allogeneic, and syngeneic transplants are most commonly used in persons with diseases affecting bone marrow, such as leukemia, aplastic anemia, and some lymphomas. The idea is to replace unhealthy marrow with healthy marrow. Sometimes a disease, such as leukemia,
interferes with the stem cell growth, causing cells to stop developing and/or become defective. Eventually these abnormal or immature cells enter the bloodstream causing serious illness. A stem cell transplant provides healthy stem cells to patients whose marrow is diseased. The transplant is actually the
transfer of healthy stem cells from a donor to a recipient.
Types of Stem Cell Collection:
Bone Marrow Stem Cell Transplant
Stem cells are collected from the patient’s or donor’s bone marrow. Historically, this has been the “traditional” transplant and requires general anesthesia in an operating room. Stem cells are collected from the hip bone. When stem cells are
collected from the bone marrow, a large needle is inserted into the back of the hipbone and marrow is withdrawn. The hip bones in the pelvis are marrow-rich bones. Since this procedure is performed under anesthesia, the donor doesn’t feel anything during the marrow collection but may experience some discomfort in the back area for a few days afterward. About 5–10% of the donor’s marrow is withdrawn, an amount that the body easily replenishes within just a few weeks. This process is known as bone marrow retrieval (sometimes referred to as a
“harvest”) and is done in an outpatient surgery center.
Peripheral Blood Stem Cell Transplant
When stem cells are taken from the circulating blood, the procedure is more like a blood 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. In order to collect them, medications known as colony stimulating 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. The growth factors are administered as injections under the skin daily for a maximum of five days duration. Once they are in the blood, these stem cells are collected in one or more sessions normally taking four to six hours each. Stem cell collections are
performed as outpatient procedures. Donors should plan to spend most of the day in the hospital on the day of collection. In this procedure, which is called apheresis, the blood circulates through a machine called a cell separator that removes the peripheral stem cells and returns the rest of the blood to the body. The stem cells are then stored and frozen until the time of the transplant for autologous bone marrow transplants. If the stem cells are collected from a related or unrelated donor, they are given immediately.
Cord Blood Transplant
Since the first cord blood transplant (CBT) in 1988, tremendous strides have been made in this field. Generally, CBT is not offered as a treatment option outside of clinical trials. It is mainly offered to children or young adults who meet the criteria for enrollment in these clinical trials. However, recently
conducted research trials have demonstrated suitability of cord blood transplants in a selected group of adult patients. Since the number of stem cells required for transplant are based on body weight, most CBT are used with patients weighing less than 90 pounds. To overcome this limitation, some transplant centers are conducting clinical trials in which two different cord
blood units are combined. There are far-reaching applications for the use of umbilical cord blood stem cells for transplant. The advantages are many. It can be frozen, stored, and readily available. Cord blood also poses a lower risk of graft-versus-host disease (GVHD) and when GVHD does occur, it seems to be milder.
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