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Bone Marrow and Stem Cell Transplantation

Introductory image: Patient and Doctor Wearing Masks at Hospital

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 and resources on bone marrow and stem cell transplantation, along with steps you can take now to find a matched donor.

Be sure to check out sessions on bone marrow and stem cell transplantation in our Online Learning Center.

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 bone marrow transplant?

A bone marrow transplant (BMT), also called a stem cell transplant, is a standard treatment option for many patients with certain life-threatening blood, immune system or genetic disorders. This treatment replaces your unhealthy blood-forming stem cells with healthy ones.

To prepare for the transplant, you are first given chemotherapy, radiation therapy or both. This treatment kills your unhealthy stem cells. It also kills the cells that make up your immune system. This keeps your immune system from rejecting the new healthy stem cells you will receive.

Once you are ready, the doctor will infuse healthy stem cells from a donor into one of your veins. These cells travel to your bone marrow and begin to grow and make the healthy blood cells your body needs. This process is called engraftment and may take two to three or even four weeks. Until the donor cells have engrafted, you stay in the hospital or are seen in a clinic so doctors can check your progress.

When should I start looking for a suitable donor?

If your doctor thinks you may be a candidate for a bone marrow/stem cell transplant in the future, start looking for a donor right away. Only about 3 out of every 10 people can find a matched related donor. And it can take a long time to find a matched unrelated donor if no related donor is available.

How does the search for a matched donor get started?

A well-matched donor is important to the success of your transplant. To look for a donor, your doctor will take a blood sample to test for your human leukocyte antigen (HLA) type. HLA are proteins found on most cells in your body. Your immune system uses these proteins as markers to recognize which cells belong in your body and which do not.

You inherit half of your HLA markers from your mother and half from your father. So each brother and sister with the same parents as you has a 1 in 4 chance of matching you. Your doctor will want to test your brothers and sisters too. Unfortunately, 7 out of 10 of patients who need a transplant don't find a matching donor in their family. If you need an unrelated donor, your primary doctor will enter your HLA data into a computer that searches the data bank of the National Marrow Donor Program (NMDP) and some other registries. This search will look for the best matched donor or umbilical cord blood unit. The best available donor may match some or all of your HLA markers. Some patients who receive unrelated donor transplants have a partially HLA matched donor.

What is a reduced-intensity transplant?

Reduced-intensity transplants use less intense treatment to prepare for transplantation than that used with higher dose "standard" regimens. They are sometimes also called non-myeloablative transplants or "mini"-transplants. It is important to understand that these are still full transplants. The toxicity is typically less than that seen with higher dose regimens. However, there is still a risk of rejection, just as after a standard transplant, and there may also be higher risks of non-engraftment and recurrence of the disease being treated. This type of transplant is generally used with older patients (over age 60) and patients with certain medical problems.

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 donor's tissue type must suitably match the patient's type. A donor can be either related or unrelated. Related donors are usually a brother or sister. If no matching family member is found, a doctor can search the registry managed by the National Marrow Donor Program.

Stem Cell Transplantation for Myelodysplastic Syndromes

Whether patients with MDS should undergo Hematopoietic stem cell transplant (HSCT) as soon as their MDS is diagnosed or wait for months or even years depends on their IPSS score. Delaying HSCT 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 HSCT right away. Also, survival after HSCT is better when patients proceed to transplant prior to progression to AML. 

Cytogenetics, or the study of abnormal chromosomes, can also affect HSCT 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 HSCT than people with primary MDS. An MDS scoring system based on cytogenetic features accurately predicts the probability of relapse and survival after HSCT 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.

Patients must receive some form of immune suppression prior to HSCT in order to alow for engraftment of donor stem cells.  Initially only high dose of chemo or radiotherapy was used to condition patient prior to HSCT, but recent newer methods have been employed with lower doses of chemo/radio therapy.  This decrease some of the toxicity of transplant but may also leaed to a higher risk of relapse.  Retrospective studies have shown equivalent overall survival in patients who are in remission at time of transplant and receive either high dose or low dose conditioning prior to HSCT.  These retrospective studies do not take into account inherent bias that may be present when assigning patients to a given conditioning regimen. A Phase III clinical trial is currently comparing the effects of more and less intensive chemotherapy treatment before HSCT on 18-month survival in patients with MDS or AML.

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 do I decide if a transplant is right for me?

It is important to think about both the risks and the benefits of a transplant. A transplant doctor can answer your questions and help you decide if a transplant is a good option.

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.[SC1] 

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 bone marrow 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.