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Sunday, November 18, 2007

Bone Marrow Transplant


Bone Marrow Transplantation
A bone marrow transplant may be used to treat patients who have a form of cancer such as leukemia, lymphoma, or breast cancer.

What is bone marrow ?
Bone marrow is the spongy tissue found inside bone. The bone marrow in the breast bone, skull, hips, ribs, and spine contains stem cells that produce the body's blood cells. The three kinds of blood cells that the body needs to function are made in the bone marrow :

a) Red blood cells carry oxygen to all parts of the body and remove wastes from organs and tissues
b) White blood cells are part of the immune system which helps your body fight infection and illness
c) Platelets help blood to clot to control bleeding

Why is bone marrow transplanted ?
In patients with certain forms of cancer, the stem cells produce an excessive number of defective or immature blood cells (as in leukemia). To eliminate the cancer, very high doses of chemotherapy and sometimes radiation therapy are given. These high-dose cancer-fighting treatments are needed to destroy the abnormal stem cells and blood cells.

However, the treatments also damage normal cells found in bone marrow. After the cancer treatments, healthy bone marrow (in the form of a transplant) is given to restore normal stem cell function. The chemotherapy not only helps destroy cancer cells but it also prepares the body to receive the transplanted marrow so it will not be rejected.

Some patients may receive a bone marrow transplant to treat aplastic anemia (in which the patient has low blood counts) and some immune deficiency diseases. Chemotherapy is given to these patients to suppress the immune system, allowing the transplanted marrow the best condition in which to grow. Without chemotherapy, the patient's own immune system would likely destroy transplanted marrow before it has a chance to function.

In a successful bone marrow transplant, the new bone marrow migrates to the large bone cavities (breast bone, skull, hips, ribs, and spine), engrafts and begins producing normal blood cells. A bone marrow transplant does not ensure that the disease will not recur; however, it can increase the chances of a cure or at least prolong the amount of time the patient is disease-free.

Who is a candidate for a bone marrow transplant ?
The decision to prescribe a bone marrow transplant is always made on an individual basis. Your doctor will consider your age, general physical condition, diagnosis, and stage of the disease. Your doctor will also make sure you understand the potential benefits and risks of the transplant procedure.

Where does the transplanted bone marrow come from ?
Bone marrow given during a transplant either comes from yourself (autologous) or from a donor whose bone marrow matches your (allogeneic).

Autologous bone marrow transplants
An autologous bone marrow transplant involves harvesting your own bone marrow, preserving and storing it in frozen form, and later, after high-dose chemotherapy and/or radiation therapy, infusing it back into your body. Autologous bone marrow transplants are possible if the disease affecting the bone marrow is in remission, or if the condition being treated doesn't involve the bone marrow (as in breast cancer).

Allogeneic bone marrow transplants
An allogeneic bone marrow transplant involves harvesting bone marrow from a family member or an unrelated donor. The harvested marrow is transplanted after you have received high-dose chemotherapy and/or radiation therapy. Whether the bone marrow donor is related or not, it must perfectly match your bone marrow.

The matching process is called human leukocyte antigen testing (HLA testing). A series of blood tests evaluate the compatibility or closeness of tissue between the donor and recipient. These test results are used to identify and compare information about your antigens (the markers in cells that stimulate antibody production) so the tissue typing lab can match a bone marrow transplant donor to you.

What happens before the transplant ?
A number of tests are performed before the bone marrow transplant procedure to make sure you are physically able to undergo a transplant. These tests also help the transplant team identify and treat any potential problems before the transplant.

Your heart, lungs, and kidney function will be tested. Blood tests, possibly a CAT scan, and a bone marrow biopsy may also be ordered by your physician. A complete dental examination is required before the procedure to minimize your risk of infection, and other precautions will be taken as necessary to minimize the risk of infection.

The tests required before the bone marrow transplant are usually done on an outpatient basis. Your transplant coordinator will help arrange these tests for you.

Central venous catheter placement
Before the bone marrow transplant can be performed, a central venous catheter is inserted through a vein in your chest during a simple surgical procedure. A central venous catheter is a slender, hollow, flexible tube (catheter) that allows fluids, nutrition solutions, antibiotics, chemotherapy, or blood products to be delivered directly into your bloodstream without frequently having to insert a needle into your vein. The catheter can also be used to collect blood samples.

Stimulating your white blood cells
Colony-stimulating factors are given before your bone marrow transplant to help your white blood cells recover from chemotherapy and reduce your risk of infection. They also increase the number of stem cells in your blood. Colony-stimulating factors are hormone-like drugs that stimulate your white blood cells to multiply, mature, and function.

Colony-stimulating factors are injected directly into your vein through an IV (intravenously) or injected into the tissue between your skin and muscle (subcutaneously) using a needle and syringe. You may need to learn how to give subcutaneous injections to yourself.

Bone marrow harvesting
Bone marrow is withdrawn through a needle inserted into a bone in the hip. This procedure is performed in the operating room and the patient is given general anesthesia (pain-relieving medication that puts you to sleep). If your own bone marrow can not be used for transplantation and if a donor is not found, peripheral stem cells may be harvested from your circulating blood.

Chemotherapy and/or radiation therapy
Very high doses of chemotherapy and/or radiation therapy are given to destroy the abnormal stem cells and blood cells. They are also given to prepare your body to receive the bone marrow transplant.

The high dose therapy has a rigorous effect on your body, wiping out your normal bone marrow. As a result, your blood counts (number of red blood cells, white blood cells, and platelets) quickly fall to low levels.

During this phase of treatment, you will be given intravenous fluids to flush out your kidneys and minimize the damage from chemotherapy. You will also be given medications to control nausea, since chemotherapy often causes nausea and vomiting.

Because you are in a fragile state of health and do not have enough white blood cells to protect you from infection, you will be isolated in your hospital room until after the new bone marrow begins to grow. Your health care providers will give you specific guidelines about the isolation procedure.

What happens during the transplant ?
The day you receive your bone marrow transplant, the harvested bone marrow is infused into a vein through an intravenous (IV) tube. The bone marrow looks like dark, thick blood. It migrates to the large bone cavities (breast bone, skull, hips, ribs, and spine), engrafts, and begins producing normal blood cells after several weeks

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