Each patient’s situation with aplastic anemia, myelodysplastic syndromes (MDS) or paroxysmal nocturnal hemoglobinuria (PNH) is unique. For some bone marrow failure disease patients, a stem cell or bone marrow transplant offers the possibility of a cure. A stem cell transplant (SCT) replaces unhealthy blood-forming stem cells with healthy ones. A stem cell transplant, is sometimes called a bone marrow transplant (BMT), or hematopoietic stem cell transplant (HSCT).
If you have a bone marrow failure disease like aplastic anemia, MDS or PNH, and your doctor thinks you may be a candidate for a bone marrow or stem cell transplant, you should start looking for a donor now. It can take a long time to find a matched donor. This section provides information about bone marrow and stem cell transplantation. There is also information and steps you can take now to find a matched donor, as well as additional information about the transplantation procedure and life after a SCT.
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What are blood-forming stem cells?
Blood cells are made in your bone marrow, a spongy tissue located inside the bones. This tissue contains parent cells called stem cells. These blood-forming stem cells make copies of themselves and produce all three types of blood cells – red blood cells, white blood cells and platelets. When blood cells are mature and functional, they leave the bone marrow and enter the blood. Healthy people have enough stem cells to keep making all the blood cells they need every day.
What is a stem cell transplant?
As early as the late 1950’s, stem cells were originally removed directly from a donor’s bone marrow and inserted directly into the patients’ blood stream. The process was called a bone marrow transplant or BMT. This treatment replaces your unhealthy blood-forming stem cells with healthy ones.Eventually scientists realized that the stem cells found in the peripheral circulation throughout the body are similar to those from the bone marrow. Use of these cells in a transplant is called a “peripheral blood stem cell transplant” (or PBSCT). The general term of “hematopoietic stem cell transplant” (HSCT) is often used and includes stem cells that can be collected from the peripheral blood, directly from the bone marrow, or even from the placenta (known as a cord blood transplant).
What are the different types of transplants?
There are two basic types of bone marrow/stem cell transplants. A transplant may use cells taken from a donor or from the patient:
- Autologous transplants use a patient's own blood-forming stem cells. These are collected from the patient's marrow or blood and frozen for later use. Autologous transplants are often not an option for patients with bone marrow failure diseases.
- Allogeneic transplants use cells from a healthy donor. The patient receives bone marrow or possibly umbilical cord or peripheral blood stem cells from another person -- usually a sibling, but sometimes an unrelated donor. The donor's tissue type must be a suitable match with the patient's type. A well-matched donor is important to the success of the transplant. The donor's tissue type must suitably match the patient's type. If no matching family member is found, a doctor can search the registry managed by the National Marrow Donor Program.
To prevent problems, the donor's stem cells should match yours as closely as possible. Donors and recipients are matched through a blood test called HLA tissue typing. People who provide their own stem cells for later use don't need to go through HLA matching.
Transplantation for bone marrow failure diseases
Aplastic anemia: Some hematologists suggest patients with non-malignant disease such as aplastic anemia, should receive stem cells from bone marrow rather than stem cells that are harvested from peripheral blood, because the incidence of graft vs. host disease is higher with peripheral blood.
PNH: Due to current advances in the treatment of PNH, transplantation may not be recommended as an initial treatment for PNH. However those PNH patients with severe bone marrow failure that does not respond to immunosuppressive therapy or those patients with thrombosis while on eculizumab, should talk to their doctor about transplantation options.
MDS: Whether patients with MDS should undergo hematopoietic stem cell transplantation (HSCT) as soon as their MDS is diagnosed or wait for months or even years depends on their IPSS score. Delaying SCT after diagnosis improves survival in patients with low-risk or intermediate-1 MDS, but survival in patients with intermediate-2 or high-risk MDS is best when they have SCT right away. Also, survival after SCT is better when patients proceed to transplant prior to progression to AML.
Cytogenetics, or the study of abnormal chromosomes, can also affect SCT outcomes. People with secondary MDS, caused by a previous treatment for another disease or disorder, tend to have more abnormal chromosomes and worse outcomes after SCT than people with primary MDS. An MDS scoring system based on cytogenetic features accurately predicts the probability of relapse and survival after SCT in patients with MDS.
Chemotherapy with cytarabine before HSCT leads to a complete response (no signs of MDS) in up to 60% of patients, especially those with normal cytogenetics. But this treatment can have serious complications and even when it works, the remission often lasts only a few months. Also, more intensive pre-transplant chemotherapy treatments have more serious side effects than less intensive regimens.
Where do doctors get healthy blood-forming stem cells to use in the transplant?
There are three sources of blood forming stem cells. These include:
- Bone marrow – Stem cells are collected from marrow inside the donor's hip bones.
- Peripheral blood stem cells (PBSC) – The donor is given a white cell growth factor that increases the production of white blood cells and also dislodges stem cells from the marrow, causing them to circulate in the blood for a while. The cells are collected from the donor's blood using a special machine.
- Umbilical cord blood – Stem cells are collected from the umbilical cord and placenta right after the birth of a baby. They are kept frozen until needed.
How does stem cell transplantation work?
While each patient has his or her own transplant experience, generally prior to the transplant, a patient will receive preparation regimens (chemotherapy and/or radiation), to prepare his or her body to receive the donated stem cells. The doctors choose the best methods based on a patient’s disease and overall health factors. Many of these treatments have potential side effects. Patients should discuss this preparation and how to handle side effects with their transplant medical team.
Once the preparation is complete, the transplant occurs. The donated stem cells are usually given to the patient through a central venous catheter, more commonly known as a central line, into the blood stream. The donated stem cells move toward the patient’s bone marrow where they begin to grow and produce new RBC, WBC, and platelets. When this happens, it is known as engraftment.
Some patients may get blood and/or platelet transfusions until the donated stem cells engraft. Neutrophils are white blood cells that help to prevent or fight off infections. A patient is a high risk for infection until engraftment occurs and his or her body starts producing new white blood cells on its own. The patient’s healthcare team will take extra precautions to help protect from or treat infections.
How do I decide if a transplant is right for me?
While it can be a cure for some patients, a SCT is a significant procedure and can cause anxiety for patients and their family members. A bone marrow transplant has serious risks. Some patients suffer from life-threatening problems as a result of their transplant. These problems can include serious infections and graft-versus-host disease (GVHD), in which the transplanted cells attack the patient's body. It is important to think about both the risks and the benefits of a transplant. Your doctor can answer your questions and help you decide if a transplant is a good option. The next step is finding a transplantation program that you are comfortable with. BeTheMatch.org provides detailed information on U.S. transplant centers as well as international transplant centers, to help you and your doctors choose the transplant center that is best for you. Many of the centers on their list are part of the National Marrow Donor Program (NMDP) network so they meet specific guidelines to help ensure you receive quality treatment.
On the other hand, a transplant may be the best hope for a cure or a longer life for some patients. It is currently the only cure for bone marrow failure diseases like aplastic anemia, MDS and PNH. You, your doctor and your family need to consider many things when making a decision, including:
- Your disease stage
- Your age
- Your overall health
- Whether a matching donor is available
- Other treatment options
How well do stem cell transplants work?
The chances the transplant will work are different for each patient. How well the transplant works depends on many things, such as:
- The disease being treated
- The stage of the disease
- The patient's age and general health
- How well the donor's tissue type matches the patient
Other things can also make a difference. It is best to talk with your doctor about your specific situation.
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