A stem cell transplant can be used for some children whose lymphoma comes back after a period of remission. It allows doctors to use higher doses of chemotherapy than would normally be tolerated.
High-dose chemotherapy destroys the bone marrow, which is where new blood cells are formed. This could lead to life-threatening infections, bleeding, and other problems because of low blood cell counts. A stem cell transplant lets doctors use higher doses of chemotherapy and, sometimes, radiation therapy. After treatment is finished, the child receives a transplant of blood-forming stem cells to restore the bone marrow.
Blood-forming stem cells used for a transplant come either from blood (for a peripheral blood stem cell transplant [PBSCT] or an umbilical cord blood transplant) or from bone marrow (for a bone marrow transplant, or BMT). Bone marrow transplants were more common in the past, but they have largely been replaced by PBSCT and cord blood transplants.
These stem cells can either be taken from the child before treatment (autologous stem cell transplant) or donated from another person (allogeneic stem cell transplant).
Autologous stem cell transplant
In an autologous bone marrow transplant (BMT) or peripheral blood stem cell (PBSC) transplant, blood-forming stem cells are removed from your child's bone marrow or bloodstream before treatment. The stem cells are carefully frozen and stored.
Your child then receives high doses of chemotherapy and sometimes radiation treatment to destroy the lymphoma cells, but this also destroys the cells in the bone marrow. The frozen stem cells are then thawed and returned to the child as a blood transfusion after the treatment.
For childhood non-Hodgkin lymphoma, this type of transplant is done more often than an allogeneic transplant.
Allogeneic stem cell transplant
A transplant using stem cells from another person is called an allogeneic stem cell transplant. This type of transplant may be used if lymphoma cells are found in a child's own bone marrow in order to avoid returning cancer cells to the child after treatment.
The donor's tissue type (also known as the HLA type) should be almost identical to the patient's tissue type to help prevent the risk of major problems with the transplant. Usually this donor is a brother or sister if they have the same tissue type as the patient. If a parent is a close match to the child, the parent's cells can sometimes be used. If there are no relatives with a good match, the cells may come from an HLA-matched, unrelated donor – a stranger who has volunteered to donate their cells – if one can be found.
The stem cells for an allogeneic SCT can come from 1 of 3 sources:
- Bone marrow: The stem cells are collected from the donor during several bone marrow aspiration procedures.
- Peripheral (circulating) blood: The stem cells are taken from the blood during apheresis. Apheresis is similar to donating blood, but instead of going into a collecting bag, the blood goes into a special machine that filters out the stem cells and returns the other parts of the blood to the person's body. This is now more common than collecting cells from the bone marrow.
- Umbilical cord blood: These stem cells are collected from the umbilical cord attached to the placenta after a baby is born and the umbilical cord is cut. (This blood is rich in stem cells.) The blood is then frozen and stored until it is needed by someone with the same tissue type. Cord blood is becoming a more common source of stem cells for children, although there are a limited number of specimens available.
How stem cells are transplanted
Stem cells collected from a donor or the patient are carefully frozen and stored. The child then receives high-dose chemotherapy and sometimes radiation treatment. This destroys any remaining cancer cells, as well as the normal cells in the bone marrow. After treatment, the frozen stem cells are thawed and returned to the body as a blood transfusion.
For the next 3 to 4 weeks the child is at high risk for serious infections because of a low white blood cell count, as well as bleeding because of a low platelet count. During this time, blood and platelet transfusions and treatment with IV antibiotics are often used to prevent or treat infections or bleeding problems.
Patients usually stay in the hospital in protective isolation (guarding against exposure to germs) until part of their white blood cell count (known as the absolute neutrophil count, or ANC) rises above 500. They may be able to leave the hospital when their ANC is near 1,000. The child is then seen in an outpatient clinic almost every day for several weeks. Because platelet counts often take longer to return to a safe level, they may get platelet transfusions as an outpatient.
Practical points
A stem cell transplant procedure is a complex treatment. If the doctors think your child may benefit from a transplant, the best place to have this done is at a nationally recognized cancer center where the staff has experience with the procedure and with managing the recovery period.
Stem cell transplants often require a lengthy hospital stay and can be very expensive (costing more than $100,000). Be sure to get a written approval from your insurer if it is recommended for your child.
Possible side effects
The possible side effects from SCT are generally divided into early and long-term effects.
Short-term side effects
The early complications and side effects are basically the same as those caused by high-dose chemotherapy (see the "Chemotherapy" section of this document), and are due to damage to the bone marrow and other quickly dividing tissues of the body. They can include low blood cell counts (with fatigue and increased risks of infection and bleeding), nausea, vomiting, loss of appetite, mouth sores, and hair loss, among others.
One of the most common and serious short-term effects is the increased risk of serious infections from bacteria, viruses, or fungi. Antibiotics are often given to try to prevent this. Other side effects, like low red blood cell and platelet counts, may require blood product transfusions or other treatments.
Long-term side effects
Some complications and side effects can persist for a long time or may not occur until years after the transplant. These can include:
- Graft-versus-host disease (GVHD), which can occur in allogeneic (donor) transplants. This happens when the donor immune system cells attack tissues of the patient's skin, liver, and digestive tract. Symptoms can include weakness, fatigue, dry mouth, rashes, nausea, diarrhea, yellowing of the skin and eyes (jaundice), and muscle aches. In severe cases, GVHD can be life-threatening. GVHD is often described as either acute or chronic, based on how soon after the transplant it begins. Drugs that weaken the immune system are often given to try to keep GVHD under control.
- Radiation damage to the lungs
- Problems with the thyroid or other hormone-making glands
- Problems with fertility
- Problems with bone growth
Be sure to talk to your child's doctor before the transplant to learn about possible long-term effects your child may have. More information on possible long-term effects can be found in the section, "What happens after treatment for non-Hodgkin lymphoma in children?"
To learn more about stem cell transplants, see our document called Bone Marrow and Peripheral Blood Stem Cell Transplants.
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