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Most stem cells are in your bone marrow. You also have some that circulate from your marrow into your blood. Bone marrow stem cells turn into red blood cells, white blood cells, or platelets to help your body stay healthy. If your bone marrow is damaged or destroyed, it can no longer make normal blood cells. In a stem cell transplant, healthy stem cells are placed in your body through an IV to help your bone marrow start to work right.
When the stem cells come from another person, it is called an allogeneic transplant. The donor may be a relative or a complete stranger. The important thing is that the donor's immune system markers are closely matched to yours. This is more likely when the donor is your brother or sister.
When the stem cells come from your own blood or bone marrow, it is called an autologous transplant.
Stem cells can also be found in your bloodstream and in the blood inside a newborn's umbilical cord.
Doctors use stem cell transplants to:
Your doctor will consider your health and your age. People who are good candidates usually are younger than 70, do not have other diseases such as heart disease or diabetes, and have a normal kidney and liver. Your doctor will also consider how much your disease has grown and how aggressive your cancer is. People with aggressive cancer that has spread to many areas of the body are not usually good candidates. Your doctor may also consider if you have cancer that has come back, such as relapsed non-Hodgkin's lymphoma or leukemia.
It depends on where the stem cells come from.
For bone marrow transplantation (BMT), a small amount of the liquid portion of the bone marrow is removed through a needle inserted into the bone. This is done many times to collect enough stem cells for the person receiving the donated bone marrow. This is called harvesting the bone marrow. The bone marrow cells are put into a blood bag. They are often frozen for future use.
For peripheral blood stem cell transplantation (PBSCT), stem cells are taken from blood. The growth factor G-CSF may be used to stimulate the growth of new stem cells so they spill over into the blood. G-CSF is a protein that is produced naturally in the body. The blood is removed from the vein and passed through a machine that takes out the stem cells. The machine then returns the remaining blood through a needle in the person's arm or through a central venous catheter. This way of collecting stem cells is called apheresis.
Stem cells may also be taken from umbilical cord blood. This is something that must be arranged with a blood bank before a baby's birth.
Doctors use chemotherapy and radiation to destroy your bone marrow. This also gets rid of the cancer cells—along with the normal cells—in your bone marrow and the rest of your body. Later, when you get healthy stem cells from a donor, those new cells will go to the marrow and be able to take over the job of making new blood cells.
A central venous catheter is inserted into your chest. The stem cells travel through the catheter into your blood, and to your bone marrow, where they will begin to produce new cells in 1 to 3 weeks. During this time:
If the donated stem cells came from bone marrow or umbilical cord blood, it usually takes about 20 days for your bone marrow to start producing new blood cells. If the donated cells came from someone's blood, it may not take that long.
You may spend 4 weeks or longer in the hospital after an allogeneic stem cell transplant. About 1 out of 4 people need to be readmitted within the first 3 months because of complications.
After you are discharged from the hospital, you will continue to see your doctor often. Because you received someone else's bone marrow, you will need treatment with medicines to prevent your immune system from attacking the donor marrow as though it were a foreign substance. You may also take medicine to help prevent the donor cells from attacking your body. Most people who do not have an immune system reaction take these medicines for 2 to 6 months.
Serious complications can occur after a stem cell transplant. They include:
When stem cells are collected from another person, the cells are tested to make sure they match your cells.
A transplant from an unrelated donor is more likely to cause problems. But improvements in the way the cells are prepared and matched and in the care of the person after the transplant have helped reduce problems. It can take 4 months or longer to find a match from an unrelated donor.
Allogeneic transplants are used to treat many diseases, including:
Allogeneic transplants are also used experimentally for other diseases, such as:
The success of a stem cell transplant depends on your age and general health, the type and stage of disease, and how well the donor matches. Serious complications can develop after a stem cell transplant.
The original disease often comes back, or relapses, after an allogeneic transplant. If relapse occurs, it can be treated with a second transplant, chemotherapy, or other treatments.
Early complications usually occur within 5 to 10 days and include:
Other possible complications include:
Serious, long-term complications include:
Healthy adults ages 18 to 60 can donate stem cells. About 17 million people worldwide are registered to be stem cell donors. Children may be donors for themselves or a brother or sister. In some cases, people who are older than 60 can donate.
If you wish to be a stem cell donor, a blood sample is taken from you and tested for tissue type. It is then compared with the tissue types of people needing a transplant. If a match is found, another blood sample will be drawn to see if your tissue type matches well enough for the transplant.
If you are selected as a stem cell donor, you will have a complete physical exam. You will also be asked questions about your health and your family history of diseases. You will also be asked to sign a consent form to have the procedure.
If you are a stem cell donor, you will receive injections of a drug called filgrastim for several days. (It is also called G-CSF, for "granulocyte colony-stimulating factor.") Filgrastim is a drug that helps your body move more white blood cells out of your bone marrow and into your bloodstream. Blood will be removed from your arm, sent through a machine to remove the stem cells, and returned to your bloodstream through your other arm.
The bone marrow collection process is a surgical procedure done under a local or general anesthetic. The procedure takes 1 to 2 hours. Bone marrow is usually removed from the back of your pelvic bone using sterile needles.
Umbilical cord blood banks have been established in some areas of the United States, Canada, and many countries in Europe to supply stem cells for related and unrelated people. Using blood from these banks decreases the time it takes to search for a match, because the samples are already typed for genetic information (HLA) and blood group and treated for infection. The match does not need to be as specific as it does with bone marrow or peripheral stem cells. Umbilical cord blood transplants also cause fewer problems with graft-versus-host disease.
Not every hospital is able to perform transplants. You may have to travel to a hospital that has special equipment and specially trained doctors and nurses.
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