A bone marrow transplant (BMT) is a procedure designed to replenish stem cells that have been destroyed by high-dose chemotherapy and/or radiotherapy.
What is Bone Marrow?
Bone marrow is a flexible, sponge-like material located inside bones. The marrow in the sternum (breastbone), pelvic bone (hips), skull, ribs, and spine contain hematopoietic (blood-forming) stem cells. Unlike embryonic stem cells, which can develop into every type of cell in the body, hematopoietic stem cells mature into on of the three types of blood cells:
- Red Blood Cells: These cells carry oxygen throughout the body.
- White Blood Cells: These cells fight infection.
- Platelets: These cells allow the blood to clot in the event of a cut or bruise.
Hematopoietic stem cells are primarily located in the bone marrow, but may also be found in the umbilical cord. Other blood-forming cells, known as peripheral blood stem cells (PBSCs), are found in the bloodstream. Stem cells extracted from the bone marrow, bloodstream, or umbilical cord can be used in transplantation procedures.
How Can Bone Marrow Transplantation Treat Cancer?
A bone marrow transplant does not kill or destroy cancer cells. However, BMT allows patients to participate in treatment strategies that would otherwise be life threatening. These strategies include high-dose chemotherapy and/or radiation therapy. Chemotherapy and radiation therapy are designed to kill and/or slow the progression of cells that divide rapidly. As a result, these therapies are used to treat cancer because cancer cells divide quickly, without control or order. Stem cells and other immature cells throughout the body also divide frequently. This means that high-dose chemo and radiotherapy will not only destroy cancer cells, but they will also destroy a patient’s healthy bone marrow.
Without healthy bone marrow, the body is vulnerable to infection, devoid of oxygen, and prone to bleeding. A bone marrow transplant restores the stem cells that have been destroyed by chemotherapy and/or radiation therapy. These transplanted cells allow the bone marrow to produce blood cells once again.
Types of Bone Marrow Transplant
Three types of bone marrow transplant have been designed to complement a variety of patient / cancer scenarios:
- Allogeneic Transplant: In this procedure, the patient receives hematopoietic stem cells from a parent or sibling. An unrelated bone marrow donor may also be used in an allogeneic transplant.
- Autologous Transplant: In this procedure, a patient’s own hematopoietic stem cells are harvested prior to chemotherapy and/or radiotherapy treatment. After treatment, these healthy stem cells are reintroduced into their body.
- Syngeneic Transplant: In this procedure, the patient receives stem cells from his or her identical twin.
What Types of Cancer are Commonly Treated with Bone Marrow Transplant?
The following cancer types are commonly treated with bone marrow transplantation:
- Lymphoma
- Leukemia
- Neuroblastoma
- Multiple Myeloma
Other types of cancer are currently being evaluated for BMT candidacy.
How are Cells Obtained for Bone Marrow Transplant?
The process of obtaining bone marrow is called “harvesting”. Allogeneic, autologous, and syngeneic hematopoietic stem cells are all harvested similarly. During the procedure, the donor receives either general anesthesia, which causes the donor to lose consciousness, or regional anesthesia, which causes a loss of sensation below the waist. After the anesthesia has become effective, a need is inserted into the pelvic (hip) bone or sternum (breastbone). Then, the bone barrow is extracted. Bone marrow harvesting usually takes about one hour.
Once the bone marrow has been harvested, it is processed to remove any blood and/or bone fragments. The processed marrow is then combined with a special preservative and frozen. This process is known as cryopreservation. Cryopreservation can keep stem cells alive for many years until they are needed again.
How Does the Patient Receive the Transplanted Cells?
Following high-dose chemotherapy or radiotherapy, the patient receives the healthy stem cells through intravenous (IV) injection. This part of a bone marrow transplant is very similar to a blood transfusion.
Side Effects of a Bone Marrow Transplant
Bone marrow transplantation is a delicate procedure that is associated with serious complications:
- Infection and/or Bleeding: The most serious concern associated with BMT is an increased vulnerability to infection and bleeding. To prevent or treat infection, the patient may receive antibiotics in addition to the BMT. To prevent bleeding, the BMT patient may receive transfusions of platelet blood cells.
- Anemia: Anemia is a condition characterized by a lack of healthy red blood cells. Red blood cells enrich the body with oxygen and iron. When the body is deprived of these essential elements, the patient may experience fatigue, dizziness, insomnia, leg cramps, pale skin, shortness of breath, rapid heart beat, and difficulty concentrating. Red blood cell transfusions are typically administered to treat anemia.
BMT patients may also experience a variety of less-severe long-term side effects that may include:
- Fatigue
- Nausea
- Vomiting
- Hair Loss
- Loss of Appetite
- Mouth Sores
- Skin Reactions
Many of the complications associated with BMT are in fact the results of either chemotherapy and/or radiation therapy. These complications include:
- Infertility
- Cataracts
- Secondary Cancer
- Organ Damage, typically affecting the kidneys, liver, lungs, and/or heart
References
- National Cancer Institute. Retrieved on May 6, 2009 from .
- American Cancer Society. Retrieved on May 6, 2009 from .
- Mayo Foundation for Medical Education and Research. 2001-2009. Retrieved on May 6, 2009 from .
- The University of Texas M. D. Anderson Cancer Center. Retrieved on May 6, 2009 from .
- WebMD, LLC. Understanding Anemia – Symptoms. Reviewed by Robert J. Bryg MD on December 14, 2008. Retrieved on May 6, 2009 from.
