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Stem Cell Transplant

bone marrow transplant

A stem cell transplant may be used so that you can have intensive high-dose chemotherapy (and sometimes radiotherapy) to kill cancerous cells. The chemotherapy is higher than conventional chemotherapy and also kills the stem cells in the bone marrow that would normally make blood cells. Therefore, following the chemotherapy, you are given back (transplanted) stem cells which can then make normal blood cells again.

Bone marrow

Blood cells are made in the bone marrow, by stem cells. Bone marrow is the soft sponge-like material in the centre of bones. Large flat bones such as the breastbone (sternum) and pelvis contain the most bone marrow.

Stem cells

Stem cells are primitive (immature) cells. There are two main types in the bone marrow - myeloid and lymphoid stem cells. These derive from even more primitive cells called common pluripotent stem cells. Stem cells constantly divide and produce new cells. Some new cells remain as stem cells and others go through a series of maturing stages (precursor or blast cells) before forming into mature blood cells.

Blood cells

Mature (fully formed) blood cells are released from the bone marrow into the bloodstream. Mature blood cells are:

  • Red cells (erythrocytes). Red cells contain a chemical called haemoglobin. This binds to oxygen, and takes oxygen from the lungs to all parts of the body.
  • White cells (leukocytes). The different types of white cells are called neutrophils (polymorphs), lymphocytes, eosinophils, monocytes, and basophils. They are part of the immune system. Their main role is to defend the body against infection.
  • Platelets. These are tiny and help the blood to clot if we cut ourselves.

Stem cells rapidly multiply to make millions of blood cells each day. Because of this they are more easily killed by chemotherapy than most other cells in the body.

When is a stem cell transplant used for treatment?

A stem cell transplant is an option which is considered for various cancer conditions. For example, for types of leukaemia, lymphoma and myeloma.
The higher doses of chemotherapy and radiotherapy that can be used in conjunction with a stem cell transplant can improve the chance of a cure for some conditions in certain circumstances.

Where are stem cells obtained from?

An autologous transplant

This means that the stem cells used for the transplant come from your own body. They are usually collected when you are free of any sign of disease (when you are in remission) following conventional chemotherapy or other treatments. The stem cells can be used soon after being collected. They can also be frozen, stored and used in the future if needed.

An allogenic transplant

This means the stem cells used for the transplant come from someone else - a donor. This is often a close relative such as a brother or sister where there is a good chance of a close match. Unrelated donors may sometimes be matched to people needing a transplant.

Stem cells can be collected:

  • From the bone marrow.
  • From the blood. The stem cells in the blood can be collected (harvested) by a machine called a cell separator. Drugs are given for a few days before this procedure to stimulate the body to make more stem cells in the bone marrow which spill out into the blood.
  • From blood taken from the umbilical cord of a newborn baby.

How is a stem cell transplant given?

It is very similar to a blood transfusion. Following the intense course of chemotherapy (and sometimes radiotherapy), the solution containing stem cells is given into one of your veins via a drip. The stem cells travel through your bloodstream and end up in your bone marrow. It can take several weeks for your bone marrow to recover, to take up the transplanted stem cells, and to make enough new blood cells. You may need several blood transfusions during this time until you are making enough blood cells. Antibiotics are given to minimize the risk of infection. Also, drugs are given to help stimulate the stem cells to multiply as quickly as possible. All this happens in an intensive care transplant unit.

What are the main risks of having a stem cell transplant?

  • Infection is the main risk. Following the intense chemotherapy, you have very low immunity. During this time you are at risk of serious and life-threatening infections.
  • Bleeding problems from the low level of platelets.
  • It you have a transplant from a donor; there is some risk that the match will not be perfect, and the donor cells may react with your body's cells. This is called graft versus host disease.
  • Rarely, the transplanted stem cells fail to work.

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