What is a bone marrow transplant?
Bone marrow transplant (BMT) is a special therapy for patients with certain cancers or other diseases. A bone marrow transplant involves taking cells that are normally found in the bone marrow (stem cells), filtering those cells, and giving them back either to the patient or to another person. The goal of BMT is to transfuse healthy bone marrow cells into a person after their own unhealthy bone marrow has been eliminated.
Bone marrow transplant has been used successfully to treat diseases such as leukemias, lymphomas, aplastic anemia, immune deficiency disorders, and some solid tumor cancers since 1968.
What is bone marrow?
Bone marrow is the soft, spongy tissue found inside bones. It is the medium for development and storage of most of the body's blood cells.
The blood cells that produce other blood cells are called stem cells. The most primitive of the stem cells is called the pluripotent stem cell, which is different than other blood cells with regards to the following properties:
Renewal--it is able to reproduce another cell identical to itself.
Differentiation--it is able to generate one or more subsets of more mature cells.
It is the stem cells that are needed in bone marrow transplant.
Why is a bone marrow transplant needed?
The goal of a bone marrow transplant is to cure many diseases and types of cancer. When the doses of chemotherapy or radiation needed to cure a cancer are so high that a person's bone marrow will be permanently damaged or destroyed by the treatment, a bone marrow transplant may be needed. Bone marrow transplants may also be needed if the bone marrow has been destroyed by a disease.
A bone marrow transplant can be used to:
Replace diseased, nonfunctioning bone marrow with healthy functioning bone marrow (for conditions such as leukemia, aplastic anemia, and sickle cell anemia).
Provide a new immune system that will fight existing or residual leukemia or other cancers not killed by the chemotherapy or radiation used in the transplant.
Replace the bone marrow and restore its normal function after high doses of chemotherapy and/or radiation are given to treat a malignancy. This process is often called "rescue" (for diseases such as lymphoma and neuroblastoma).
Replace bone marrow with genetically healthy functioning bone marrow to prevent further damage from a genetic disease process (such as Hurler's syndrome and adrenoleukodystrophy).
The risks and benefits must be weighed in a thorough discussion with your doctor and specialists in bone marrow transplants prior to procedure.
What are some diseases that may benefit from bone marrow transplant?
The following diseases are the ones that most commonly benefit from bone marrow transplant:
Severe aplastic anemia
Immune deficiency disorders
Some solid-tumor cancers
However, patients experience diseases differently, and bone marrow transplant may not be appropriate for everyone who suffers from these diseases.
What are the different types of bone marrow transplants?
There are different types of bone marrow transplants depending on who the donor is. The different types of BMT include the following:
Autologous bone marrow transplant
The donor is the patient himself or herself. Stem cells are taken from the patient either by bone marrow harvest or apheresis (a process of collecting peripheral blood stem cells), frozen, and then given back to the patient after intensive treatment. Often the term "rescue" is used instead of "transplant."
Allogeneic bone marrow transplant
The donor shares the same genetic type as the patient. Stem cells are taken either by bone marrow harvest or apheresis from a genetically-matched donor, usually a brother or sister. Other donors for allogeneic bone marrow transplants may include the following:
A parent--a haploid-identical match is when the donor is a parent and the genetic match is at least half identical to the recipient. These transplants are rare.
Unrelated bone marrow transplants (UBMT or MUD for matched unrelated donor)--the genetically matched marrow or stem cells are from an unrelated donor. Unrelated donors are found through national bone marrow registries.
Umbilical cord blood transplant
Stem cells are taken from an umbilical cord immediately after delivery of an infant. These stem cells reproduce into mature, functioning blood cells quicker and more effectively than do stem cells taken from the bone marrow of another child or adult. The stem cells are tested, typed, counted, and frozen until they are needed for a transplant.