Types of Bone Marrow Transplants
The name for what is being transplanted in a bone marrow or stem cell transplant has changed over the years. The cells that are being transplanted are stem cells that are made in the bone marrow. These stem cells are immature cells that grow into mature red blood cells, white blood cells, platelets, or plasma cells. Stem cells are an essential part of your immune system.
Names you may hear for transplants include:
- Bone marrow transplant
- Marrow transplant
- Peripheral blood stem cell transplant
- Stem cell transplant
- Hemopoietic cell transplant
- Hemopoietic progenitor cell transplant
- Pluripotent stem cell transplant
- Nonmyeloablative, or mini-transplant
In each case, doctors are transplanting stem cells.
There are five types of transplants. The difference between the types of transplants has to do with the source of the transplanted cells. The type of transplant your child receives depends on his or her situation.
- Autologous transplant—Transplanted cells come from the body of the transplant recipient.
- Allogeneic transplant—Transplanted cells come from a donor who may be related to the recipient (a family member) or unrelated.
- Syngeneic transplant—Transplanted cells come from an identical twin sibling. (This is a type of allogeneic transplant.)
- Cord blood—Transplanted cells come from the umbilical cord and placenta after a baby is born. This blood is rich in blood-forming cells. (This is a type of allogeneic transplant.)
- Mixed chimerism transplant—Transplanted cells come from either a related or unrelated donor. The transplant takes place after the recipient has a moderate dose of chemotherapy and radiation to set up a mixed immune system. This type is also called a mini-transplant or nonmyeloablative transplant. (This is a type of allogeneic transplant.)
The Advantage of an Autologous Transplant
The advantage to using the child’s own stem cells is that he or she will not face the complications of graft-versus-host disease. However, with an autologous transplant the child does not have the same graft-versus-tumor benefits. As a result, there is a higher relapse rate with autologous transplants, and this type is not suitable for a number of diseases.
Tissue Matching for an Allogeneic Transplant
If your child has an allogeneic transplant, our doctors will pick a donor whose tissue most closely matches your child’s tissue. The closer the match, the greater the chances for a positive outcome. If your child does not have a closely matched relative who can donate bone marrow or stem cells, we will work with the national registries to find an unrelated donor.
Before doctors transplant hematopoietic cells, recipients undergo an intensive regimen of chemotherapy (and sometimes radiation, too) to remove their bone marrow, the source of their problematic cells—for instance, cancerous cells in the case of leukemia and sickle-prone cells in the case of sickle cell disease. The pretransplant regimen is called “conditioning.” Standard conditioning regimens can cause numerous side effects, some quite serious.
“Until recently, patients have not had other options except for a standard transplant,” says Ann E. Woolfrey, MD. But since the late 1990s, doctors have used mini-transplants, or nonmyeloablative transplants, for some patients.
Mini-transplants, involve a less-intensive conditioning regimen, that relies on graft-versus-tumor effects, rather than high-dose chemotherapy or radiation therapy, for killing the patient’s problematic cells. Doctors at SCCA and the Hutchinson Center may use this type of transplant for nonmalignant diseases as well as for cancer. “We pioneered use of the nonmyeloablative transplant in nonmalignant diseases,” says Dr. Woolfrey. “We have shown that this new procedure is very successful in reducing the risks of the transplant.”
Nonmyeloablative procedures weaken the patient’s immune system so it accepts the donor’s stem cells and ideally, the transplanted cells will engraft, or establish themselves in the recipient’s body, and begin producing blood cells, taking over for the disabled marrow. Mini-transplants have reduced infections, reduced the need for blood transfusions, and reduced heart, lung and liver problems—all possible complications of the standard conditioning regimen.
Dr. Woolfrey is now developing a nonmyeloablative transplant protocol to reduce the severity of graft-versus-host disease, in which transplanted cells regard the recipient’s cells as foreign and attack them.
If your child has a bone marrow transplant, he or she will receive bone marrow that has been collected from a donor. The donor may be a family member or an unrelated donor whose tissue type closely matches your child’s tissue.
The doctors collect bone marrow from the hip using large needles. The procedure (called bone marrow harvesting) takes about two hours and is performed on the day of transplant while the donor is sedated under anesthesia. Most donors do not need to stay at the hospital overnight. If your donor is a family member who comes with you to Seattle, this procedure will be done at Seattle Children’s or at University of Washington Medical Center, both Seattle Cancer Care Alliance (SCCA) partners.
If your donor is an unrelated adult who is not in Seattle, the bone marrow harvest will be done at a hospital close to where the donor lives, and then the marrow will be hand-carried to SCCA.
Your child will receive the bone marrow cells by infusion in a procedure that is similar to receiving a blood transfusion. This takes several hours and is not painful.
Stem cells are produced in the bone marrow and circulate in the bloodstream. Circulating stem cells are called peripheral blood stem cells (PBSCs). If your child has a stem cell transplant, he or she will receive stem cells that have been collected from the blood of the donor—who may be your child (autologous transplant) or a sibling, another relative or a closely matched, unrelated donor (allogeneic transplant).
An autologous stem cell transplant donor may be of any age, but an allogeneic stem cell transplant donor must be older than the age of 12.
Before collection, the donor will need to receive several days of daily injections of special proteins called growth factors (G-CSF). These injections encourage stem cells to enter the blood from the bone marrow.
We do PBSC collection in the Apheresis Unit on the fifth floor of the SCCA clinic. The procedure takes several hours, usually over one or two days.
During PBSC collection, the donor’s blood is withdrawn and circulated through a machine that separates out the stem cells and returns the remaining blood cells to the donor. For an autologous transplant, the collection is painless for the donor, who has blood withdrawn through a central intravenous catheter. For an allogeneic transplant, there may be some pain when needles are inserted into the donor’s arms to collect the cells. The donor can watch TV or read during this time. If the donor is a child, parents are encouraged to bring along favorite videos, games, or other quiet activities.
If the donor is an unrelated adult who is not in Seattle, the PBSC collection will be done at a hospital close to where the donor lives, and then the cells will be hand-carried to SCCA.
Like bone marrow, umbilical cord blood contains stem cells. It comes from the umbilical cord of newborn infants and is removed from the placenta after birth and then stored. Once a cord blood match has been identified through the cord blood registry, the cord blood is shipped to SCCA.