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Bone Marrow
Transplant
Over the past decade, bone
marrow transplant has evolved from an experimental procedure for patients with leukemia
into a rapidly expanding area of clinical investigation that offers high cure rates for
patients with more than 60 previously fatal diseases - including several types of cancer.
Bone marrow is found in the cavities of
the body's bones. It is a substance resembling blood that produces the body's blood
components, including red blood cells, platelets, and white blood cells - the main agents
of the body's immune system. Marrow transplants are used to treat patients whose marrow
stops producing the correct amounts of various blood cells. Marrow cells also circulate in
the peripheral blood and can be obtained from that source.
- Allogeneic: Marrow that is
genetically similar to the patient's marrow is harvested from a relative or donor who is
unrelated to the patient.
- Autologous: The patient's
own marrow is used. A small amount of marrow is removed, sometimes "purged" of
cancerous cells and reinfused.
- Syngeneic: The donor is an
identical twin of the recipient.
Bone marrow transplantation is a
technologically advanced process that follows these four steps:
- Bone marrow (approximately 700
milliliters) is harvested from the pelvic bone of a compatible donor. In the case of an
autologous transplant, a small amount of the patient's own marrow or peripheral blood is
removed and treated to kill cancerous cells.
- The patient receives massive doses of
chemotherapy and radiation that destroy the remaining bone marrow.
- To rescue the patient, reserved or donor
marrow or peripheral blood is delivered intravenously to rescue the patient. The process
of infusion is much like a blood transfusion. The marrow cells find their way through the
bloodstream to the center of the long bones.
- Supportive therapy with blood products,
cyclosporine, antibiotics and anti-viral drugs allows many patients to recover from the
severe, induced neutropenia (a reduction in the blood granulocyte count that leaves
patients susceptible to infection). This therapy also helps "regrow" the new
bone marrow that patients need for a properly functioning immune system.
- Diseases treated with BMT include
Diseases treated include acute
lymphoblastic leukemia, acute myeloid leukemia, chronic myelocytic leukemia, Hodgkin
disease and non-Hodgkin lymphoma, thalassemia major, neuroblastoma, severe combined a
immunodeficiency, Fanconi pancytopenia syndrome, Wiskott-Aldrich syndrome, congenital
hypoplastic anemia, chronic granulomatous disease, metabolic storage disorder,
osteogenesis imperfecta.
Selection and growth of stem cells, the
origin of all blood cells, is under study. This procedure would repopulate the patient's
body with red blood cells, platelets, lymphocytes and other types of cells that form the
body's blood and immune system.
New anti-rejection drugs are being used
that will be more effective than current drugs and cause fewer side effects.
Monoclonal antibodies are used to destroy
specialized bone marrow cells in the donor's marrow that might otherwise hurt the
transplant recipient. Monoclonal antibodies allow less perfectly matched donor marrow to
be used.
Cell and gene therapy for inherited
disorders and for malignant diseases are being combined with marrow transplantation to
increase the effectiveness of the process.
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