There are three sources in the body from which stem cells for a transplant are collected: the bone marrow, the peripheral blood (blood circulating around the body), and umbilical cord blood. (Whether the stem cells are collected from your child who needs a transplant or from another person is discussed in Types of Transplants.
The bone marrow is the main production site of young stem cells. Doctors collect bone marrow from the pelvic bone (hip) using large needles. The procedure (called bone marrow harvesting) takes about two hours and is performed while the donor is sedated under anesthesia. Most donors do not need to stay at the hospital overnight.
If your child’s 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) treatment sites. If your child’s 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. The collection of stem cells from bone marrow typically occurs within a day of the transplant.
Stem cells are produced in the bone marrow and then circulate in the bloodstream. Circulating stem cells, called peripheral blood stem cells (PBSCs), can be collected from the blood of the donor in a process called apheresis. If the collected PBSCs are to be donated to another person (rather than put back into the same person after conditioning), the donor must be older than age 12.
Before collection by apheresis, the donor receives several daily injections of naturally occurring proteins called growth factors (G-CSF). These injections encourage (“mobilize”) stem cells to enter the blood from the bone marrow. A few days later, the stem cells are collected using a machine similar to that used for blood donation at blood banks. The donor’s blood is withdrawn and circulated through the machine, which separates out the stem cells and returns the remaining blood cells to the donor.
We do PBSC collection in the Apheresis Unit on the fifth floor of the SCCA outpatient clinic on Lake Union. The collection typically takes a few hours, and donors leave the same day.
For those who are donating blood for their own transplant, the collection is painless because the blood is withdrawn through an already-placed central venous catheter. For those donating PBSCs for another person, there may be some pain when needles are inserted into the arms. The donor can watch TV or read during apheresis. If the donor is a child, parents are encouraged to bring along favorite videos, games, or other quiet activities.
If the child’s 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.
The collection of stem cells from peripheral blood typically occurs within a day of the transplant.
Like bone marrow, umbilical cord blood contains stem cells. The cord blood is collected at the time of a baby’s birth with no risk to the infant or mother. After the umbilical cord is cut, a needle is inserted into the vein of the umbilical cord, and the leftover blood from the placenta and umbilical cord is collected, frozen, and stored for future use. Once a cord blood match has been identified through the cord blood registry, the cord blood is shipped to SCCA.
The advantage of using cord blood is that the stem cells are still quite immature. This reduces the chance of bad effects between the transplanted cells and the recipient’s cells. Thus, this “universal donor” blood can be used for virtually any child who is unable to find a match.
The main disadvantage of using cord blood is that fewer stem cells are available for transplantation. And when fewer stem cells are transplanted, these cells take longer to engraft and start functioning normally. This increases the risk of infection as the child recovers in the hospital.
SCCA doctors are developing special methods to increase the number of cord blood stem cells given during a transplant. In one new method, the child receives two units of cord blood instead of one. In the other, the doctors use a special protein to stimulate the stem cells to multiply in the lab before the transplant. If your child cannot find a good match, SCCA transplant specialists can tell you more about clinical studies with these new cord blood methods.