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Also known as a BMT, stem cell transplant, or hematopoietic stem cell transplant
Bone marrow is found in the center of bones and is where blood cells are made. It is found in the spongy part of the bones, especially the hips, ribs, breastbone, and spine. Bone marrow contains the youngest type of blood cells known as hematopoietic stem cells. As a hematopoietic stemcell ages, it becomes a white cell, red cell, or platelet. Hematopoietic stem cells are found in bone marrow, peripheral blood (bloodstream), and umbilical cord blood.
A bone marrow transplant (BMT) replaces diseased or damaged cells with non-cancerous stem cells that can grow healthy, new cells. BMT is usually used when cancer treatments have destroyed normal stem cells in the bone marrow. The stem cells can be replaced through BMT. A BMT is also performed when the chances for cure with chemotherapy alone are low.
There are two major types of BMT, and the type that your child will receive depends upon the diagnosis.
The first step is to locate a donor whose blood cells closely match the patient's. This is done by tissue typing prospective donors. Tissue typing is done by a blood sample and is called HLA typing, which stands for Human Lymphocyte Antigens. These antigens are found on the surface of white blood cells. A patient's full siblings each have a 25% chance of being a tissue type match. Less commonly, a parent may match the patient. Occasionally, a less- than-perfectly matched related donor is used.
If a related donor is not available, then a search for a compatible, unrelated donor is performed through the National Marrow Donor Program. Unrelated donor cells can come from a living donor or frozen cord blood. Your physician will decide what the best source for donor cells is for your child. This is based upon urgency of the transplant, weight of your child, and the best tissue type match. An unrelated donor search may take several months; cord blood can be obtained within a few weeks.
Peripheral stem cells are usually collected for autologous transplant, but stem cells from the bone marrow also can be used. These are collected either before the patient has chemotherapy or following a course of chemotherapy. To collect peripheral stem cells, the patient receives medications (such as G-CSF and/or GM-CSF) to increase the number of peripheral blood stem cells available.
Cells are collected through a process called apheresis. An apheresis machine has a circuit that will collect blood, separate, and remove white blood cells containing stem cells, and then return red blood cells to the patient. This process takes about 4 hours and may need to be repeated for 2 or 3 days in a row. For certain diseases, the peripheral blood stem cells may be treated with anticancer medications to prevent tumor cells from being placed into back into the patient's body.
Before the transplant admission:
When the healthcare team decides that BMT is the best treatment option for your child, they will schedule a lengthy conversation with you to explain the procedure. They will explain the many risks associated with BMT, as well as what you can expect before, during, and after the transplant.
Your child will undergo testing to make sure he/she is healthy enough to withstand the rigors of transplant. Testing will include evaluation of the heart function with electrocardiogram (ECG) and echocardiogram, lung function (if your child is old enough), kidney and liver function, and infection status. Depending upon the disease, a bone marrow aspirate and spinal tap may be performed.
When your child is deemed healthy enough for BMT, physicians will usually insert a central line catheter that allows easy access to a large vein in the chest. The catheter will be used to deliver the new stem cells, as well as blood, antibiotics, and other medications during treatment.
Preparation Before Transplant:
Your child will be given preparative treatment, called "conditioning" before the transplant. Conditioning includes high doses of chemotherapy and sometimes, radiation of the whole body. The type and purpose of conditioning depends upon your child's underlying diagnosis but may include:
Commonly used drugs include:
Once conditioning is complete, stem cells are given through a catheter. This is very similar to a blood transfusion. After traveling through the bloodstream to the bone marrow, the transplanted stem cells will begin to make red and white blood cells, and platelets.
It can take between 14 and 30 days for enough blood cells, particularly white blood cells, to be created so the body can fight infection. The identification of new blood cells and an increase in white blood cells following BMT is called engraftment. Until then, your child will be at a high risk for infection, anemia, and bleeding. Your child will remain in the hospital until he or she is well enough for discharge.
Outpatient follow-up is essential after discharge, as the risk of infection and other complications persist. Although the risk of relapse (recurrence of the cancer) is less with a transplant than chemotherapy, relapse may still occur. Most relapses occur within several years after a transplant.
The process of BMT places a tremendous amount of strain on the body during conditioning, the actual transplant, and in the days following transplant. Your child's immune system will basically be eliminated during conditioning. As a result, your child will be at high risk for infection and blood-related side effects immediately following transplant. Careful monitoring, use of medicines to treat or prevent infections, and other forms of supportive care can help your child to feel as comfortable as possible.
Infection is very common before, during, and after transplant.
Anemia (low red blood cells) and thrombocytopenia (low platelets). Transfusions of red blood cells and platelets will be needed until the new cells increase sufficiently to make these.
Mucositis (sore mouth, sore throat). IV fluids or nutrition and pain medicines are used to help with these symptoms. This problem usually improves as the new cells grow in the patient.
Loss of appetite, nausea. IV nutrition and/or nutrition with a tube into the stomach are used so that weight loss doesn't occur. Medications can be given to prevent or reduce nausea.
Infection - The patient's immune system is destroyed after a transplant, and it takes many months and sometimes years to return. The types of infections that may occur include: bacterial, fungal, and viral. Preventive antibiotics are given for some patients. Special precautions are taken to protect your child from infection, including limiting visitors and avoiding crowded areas (such as stores) after discharge.
Graft vs. host disease (GVHD) - This occurs only in an allogeneic blood or marrow transplant. Certain types of donor cells, called T cells (or T lymphocytes) react to the patient’s body and recognize it as "foreign." Medicines are given post-transplant to prevent this complication, but it may occur despite this.
Organ toxicity - Conditioning and prior cancer treatment may damage the lungs, liver, kidneys, and heart. These effects are unpredictable and not all children recover from organ toxicity.
Late Effects - There is a very good chance that there will be long-term effects following BMT that may not be identified until years after treatment. These include: