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A bone marrow transplant (BMT) is the removal of bone marrow
from one person and the return of its blood-forming cells
later to the same person or the transfer of the blood-forming
cells to someone else. It is a relatively new medical procedure
used to treat diseases such as leukemia, aplastic anemia,
Hodgkin's disease, multiple myeloma, immune deficiency disorders,
and some solid tumors.
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Bone marrow is
the soft, sponge-like tissue found within the cavities
of bones that contain fat and blood-forming tissue. It
contains immature cells called stem cells that produce
the body's blood cells. These blood cells include: white |
blood cells (leukocytes), which fight infection; red blood cells
(erythrocytes), which carry oxygen to, and remove waste products
from, organs and tissues; and platelets, which enable the blood
to clot.
Healthy bone marrow tissue constantly renews the blood supply
and is essential to life. Unfortunately, the amount of drugs
or radiation needed to kill cancer cells also destroys bone
marrow. Bone marrow transplantation is often used as a rescue
procedure, replacing stem cells that have been destroyed by
high doses of chemotherapy and/or radiation therapy. In some
cancers, particularly those involving the blood cells, bone
marrow transplantation is used to attack the malignancy directly.
Acute leukemia, for example, was the first cancer to be successfully
treated with bone marrow transplantation.
The transplant procedure begins with the patient or donor
providing stem cells. These blood-forming cells are stored
while the patient's cancer cells are destroyed by chemotherapy
drugs and/or radiation. The stem cells are then returned to
the patient to speed the recovery of bone marrow.
Most bone marrow transplantation procedures are successful.
The recipients are discharged promptly from the hospital after
they have recovered. The long-term response rate varies greatly
depending on the type and stage of cancer.
There are three types of transplants according to the source
of the bone marrow. An autologous transplant is the removal
of bone marrow from the person with cancer before treatment
and is returned to him/her after treatment with high doses
of chemotherapy or radiation therapy or both. In syngeneic
transplants, patients receive stem cells from their identical
twin. An allogeneic transplant is donated by someone other
than the patient or an identical twin. Siblings are always
a closer match than parents and more likely to be compatible
than other family members. The best matches also come from
someone of the same ancestry.
As with some other cancer therapies, bone marrow transplants
may also cause side effects, which should be recognized and
effectively managed.
Almost everyone who undergoes bone marrow transplant experiences
lethargy, nausea, and vomiting because of the high doses of
chemotherapy and/or radiation that precede the transplant.
Infection is an early serious danger for the patient, so the
patient is closely monitored for fever and other signs of
infection. Some patients may develop veno-occlusive disease,
a very serious disease of the liver. Another major risk of
bone marrow transplant is that the recipient's immune system
may reject the transplanted "foreign" marrow.
Despite the risk involved with bone marrow transplant, the
procedure is still recommended by doctors and opted for by
cancer patients as an effective weapon against cancer. Most
cancer patients receiving them benefit greatly from successful
bone marrow transplants. Unfortunately, many insurance plans
do not cover bone marrow transplantation, and the high cost
of this treatment is often the reason why BMT is not often
performed.
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