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A hematopoietic cell transplant is a medical procedure used to treat a variety of diseases, including childhood cancer. It replaces damaged or destroyed blood-forming (hematopoietic) cells with healthy blood-forming cells.
Since the main source of blood-forming cells is the bone marrow, the procedure has traditionally been referred to as a bone marrow transplant. As advances have been made, the term hematopoietic cell transplant has grown in popularity. The terms are often used in place of each other. Some people may also call the process a stem cell transplant.
A transplant can successfully treat certain childhood cancers, but it can have serious side effects and late effects. It is an option to consider carefully. Having a transplant is not an easy process. It is taxing physically and emotionally for both the patient and family caregivers. But there are many people on the transplant care team to support patients and families along the way. Many children and teenagers who have had transplants are now living active, cancer-free lives.
Bone marrow is a soft, spongy material that is in the center of most of the body’s bones. Large numbers of blood-forming (hematopoietic) cells live in the bone marrow.
Hematopoietic cells are the parents of all other blood cells. They mature into cells that eventually become:
The bone marrow works like a blood cell factory, constantly making new hematopoietic cells so that the red blood cells, white blood cells, and platelets circulating in the blood can do their jobs.
All red blood cells and platelets are manufactured in the bone marrow, along with about 70 percent of white blood cells. (The other 30 percent are produced by the spleen, lymph nodes, and thymus gland.)
Very small numbers of hematopoietic cells can also be found in the peripheral (circulating) blood. Umbilical cord blood is also a source of blood-forming cells.
The goal of transplant is to:
In pediatric cancer, transplant is primarily used to treat leukemia, usually when standard treatment for the cancer has failed. Leukemia, cancer of the blood and bone marrow, causes the body to produce damaged white blood cells, which makes the patient very sick.
There are basically two types of transplants:
Transplant is a physically challenging medical procedure. The medical team will first determine if the patient is a suitable candidate by considering the patient’s:
To ensure the patient can tolerate a transplant, the patient will also have tests on his or her heart, lungs, kidneys, and other vital organs. These tests typically include:
If they don’t already have one, patients will receive a central line so they won’t have frequent needle sticks.
The transplant team at the hospital will coordinate the donor search. A sibling with the same biological parents is usually the first choice because the donor’s and patient’s hematopoietic cells must have similar genetic markers. These markers are proteins called human leukocyte antigens (HLA). Determining whether or not someone is an HLA match requires an HLA test, which involves taking a sample of the patient and potential donor’s blood. In some cases, an inner cheek swab sample can be used for this test. The cells are then sent to a laboratory for testing.
Since these genetic markers are inherited from parents, a brother or sister is the most likely match. If the patient and sibling have the same biological parents, each brother and sister has a 25 percent chance of being an HLA match to the patient. Because of this, about 70% of patients will not have a matched sibling donor available.
If there is no matched sibling, then the care team will search for an unrelated donor or cord blood unit (if the transplant center performs cord blood transplants) through the Be the Match® Registry of the National Donor Marrow Program. About 30 percent of patients find a matched unrelated donor.
If a perfect match cannot be found, the doctor may suggest using a mismatched donor, which is a donor who is a close, but not exact, HLA match. Mismatched donor transplants are fairly common, and many are successful.
For patients who can’t find a suitable donor who is a close match, in some cases it is possible to use bone marrow or peripheral hematopoietic cells from a family member who is a “half-match.” This type of transplant is called a haploidentical (half-matched) bone marrow transplant.
Donors must also be medically capable of serving as a donor. The donor center, through Be the Match, will screen the potential donor for certain health conditions:
Blood-forming cells can be collected from bone marrow, peripheral (circulating) blood, and from the blood of donated umbilical cords. This process is called harvest.
Many patients think a transplant is a complicated surgical procedure, but the transplant itself is a relatively simple process. It is much like a blood transfusion. Donor cells are in a bag or syringe that is connected through a tube to the patient’s central line. It only takes a few minutes to a few hours and is not painful.
After entering the bloodstream, the hematopoietic cells travel to the bone marrow, where they begin to divide and become white blood cells, red blood cells, and platelets in a process known as engraftment. Engraftment usually happens in 2-4 weeks (longer if the source was an umbilical cord.) Complete recovery of the immune system may take several months for autologous (using patient’s own cells) transplant to 6 months or a year for allogeneic (using related or unrelated donor cells) transplant.
Doctors evaluate the results of various blood tests to confirm that new blood cells are being produced (engraftment) and that the cancer has not returned. After the transplant, patients have blood drawn daily so it can be tested in the lab. Doctors will count how many red blood cells, white blood cells, and platelets are in the body. Since they are counted each day, doctors and patients can keep track of the progress. Because everyone is different, engraftment can happen at different times. Usually it takes two weeks to a month. White blood cells are the first to engraft, followed by red blood cells and then platelets. Patients may need transfusions of red blood cells and platelets to keep counts in a safe range while they wait on engraftment to take place.
Bone marrow aspiration (the removal of a small sample of bone marrow through a needle for examination under a microscope) can also help doctors determine how well the new blood-forming cells are working, and if the cancer is in remission.
When patients leave the transplant unit, they still have weakened immune systems and will have difficulty fighting infections. Some of these infections can be life-threatening. After discharge, patients will need a caregiver at home with them until their immune systems return to normal, a process that can take from a few months to a year.
Tell the transplant clinic staff immediately if the patient’s main caregiver will change. It’s good to plan the change in advance. A transplant staff member must train each caregiver.
The two conditions that cause the most serious side effects and late effects are graft rejection and graft vs. host disease (GVHD).
Caregivers should call the patient’s local doctor or their transplant unit’s doctor or nurse practitioner immediately if the patient has one or more of the following symptoms:
Because of the physical side effects and being separated from family, friends, and normal routines, patients may have periods of sadness or depression. It is OK to have a day or two of feeling sad, but if these feelings last longer patients should talk to a member of their care team. It could be their doctor or nurse or perhaps their social worker, chaplain, psychologist, or child life specialist.
Some of the complications associated with a transplant are known as late effects, because they are not apparent until several months or even years after treatment. Most of them resolve with time, but others may be permanent and need long-term attention.
Late effects of transplant may include:
No one experiences all of these problems. Risk for developing problems after transplant will depend on your disease, type of transplant you had, your age and prior treatment history. Many complications are preventable with proper screening and preventive measures. Regular doctor’s appointments are very important.
Patients are observed for a long time after transplantation to determine whether side effects are present. Patients who underwent total body irradiation to prepare for transplant are at risk of endocrine (gland) problems that include hypothyroidism, adrenal insufficiency or growth hormone insufficiency. It is important that the patient’s height and weight be recorded regularly and, if necessary, monitored by an endocrinologist.
In some cases, the cancer may come back (relapse) after the transplant. Relapse is most common in the first year after transplant and the risk decreases as time goes by. The transplant team will continue to care for you and will discuss other treatment options. These could include clinical trials or another transplant.
Reviewed: June 2018