Bone marrow transplant

What is bone marrow transplant?

Bone marrow transplant is a procedure in which healthy bone marrow is transplanted into a patient whose bone marrow is not functioning properly. Problems in bone marrow are often caused by chemotherapy or radiation treatment for cancer. This procedure can also be done to correct hereditary blood diseases. The healthy bone marrow may be taken from the patient prior to chemotherapy or radiation treatment (autograft), or it may be taken from a donor (allograft).

What is bone marrow?

Bone marrow is the soft, sponge-like material found inside bones. It contains immature cells called stem cells that produce blood cells. There are three types of blood cells: white blood cells, which fight infection; red blood cells, which carry oxygen to and from organs and tissues; and platelets, which enable the blood to clot.

Why is it done?

If a patient develops a disease of the blood cells, especially cancers such as leukaemia, he may require high doses of chemotherapy to destroy the cancer. However, this also destroys normal blood cells.

Alternatively, hereditary or acquired disorders may cause abnormal blood cell production. In these cases, transplantation of healthy bone marrow may save a patient's life. Transplanted bone marrow will restore production of white blood cells, red blood cells, and platelets.

What is the procedure?

Bone marrow transplant patients are usually treated in specialised centres and the patient stays in a special nursing unit (a bone marrow transplant unit) to limit exposure to infections. The hospitalisation period is from 4 to 6 weeks, during which time the patient is isolated and under strict monitoring because of the increased risk of infection and/or bleeding.

Donated bone marrow must match the patient's tissue type. It can be taken from the patient, a living relative (usually a brother or a sister), or from an unrelated donor. Donors are matched through special blood tests called HLA tissue typing.

Bone marrow is taken from the donor in the operating room while one is unconscious and pain-free (under general anaesthesia). Some of the donor's bone marrow is removed from the top of the hip bone. The bone marrow is filtered, treated, and transplanted immediately or frozen and stored for later use. Then, transplant material is transfused into the patient through a vein and is naturally transported back into the bone cavities where it grows to replace the old bone marrow.

Alternatively, blood cell precursors, called stem cells, can be induced to move from the bone marrow to the blood stream using special medications. These stem cells can then be taken from the bloodstream through a procedure called leukapheresis.

The patient is prepared for transplantation by administering high doses of chemotherapy or radiation (conditioning). This serves two purposes. First, it destroys the patient's abnormal blood cells or cancer. Second, it inhibits the patient's immune response against the donor bone marrow (graft rejection).

Following conditioning, the patient is ready for bone marrow infusion. After infusion, it takes 10 to 20 days for the bone marrow to establish itself. During this time, the patient requires support with blood cell transfusions.

What are the indications?

Bone marrow transplant may be recommended for:
Bone marrow deficiency disease caused by:

• abnormal red blood cell production, such as thalassaemia or sickle cell disease
  
• aggressive cancer treatments (chemotherapy, radiation therapy), especially for leukaemia or lymphoma
  
• lack of normal blood cell production (aplastic anaemia)
  Immune system disorders (immunodeficiency) such as:
  
• congenital neutropenia
  
• severe combined immunodeficiency syndrome

Bone marrow transplant is not recommended for:

• patients with heart, kidney, lungs, or liver disorders
  
• patients with other diseases that may limit survival

What are the risks?

The risks for any anaesthesia are:

• reactions to medications
  
• problems breathing

Chemotherapy given prior to bone marrow transplant (conditioning) can cause significant toxicity, such as mouth sores, diarrhoea, liver damage, or lung damage. While waiting for bone marrow to grow, the patient is at high risk for infection as also bleeding.

The major problem with bone marrow transplants (when the marrow comes from a donor, not the patient) is graft-versus-host disease. The transplanted healthy bone marrow cells may attack the patient's cells as though they were foreign organisms. In this case, drugs to suppress the immune system must be taken, but this also decreases the body's ability to fight infections.

Other significant problems with a bone marrow transplant are those of all major organ transplants - finding a donor and the cost. The donor is usually a sibling with compatible tissue. The more siblings the patient has, the more chances there are of finding a compatible donor.

What is the prognosis?

Bone marrow transplant prolongs the life of a patient who would otherwise die. Relatively normal activities can be resumed as soon as the patient feels well enough and after consulting with the doctor.

The patient will require attentive follow-up care for 2 to 3 months after discharge from the hospital. It may take 6 months to a year for the immune system to fully recover from this procedure.