Stem cell transplant

Find out about stem cell transplants for chronic myeloid leukaemia (CML) and how a donor is chosen.

The aim of a stem cell transplant is to try to cure your CML, or control it for longer. You might have a transplant if your CML is no longer responding to targeted cancer drugs, such as imatinib, nilotinib and dasatinib.

A stem cell transplant is also called a peripheral blood stem cell transplant. Stem cells are very early cells in the bone marrow that develop into the following types of blood cell:

Diagram of three different types of blood cell

You have a stem cell transplant after very high doses of chemotherapy and sometimes whole body radiotherapy. The chemotherapy and radiotherapy has a good chance of killing the cancer cells but also kills the stem cells in your bone marrow.

For CML, you usually have a stem cell transplant using stem cells from a donor. This is called an allogeneic transplant. By having someone elses bone marrow it means you have a different immune system which can help destroy the CML cells. 

Having stem cells from a donor

Your donor stem cells

The stem cells of your donor need to be as similar as possible to yours.

The most suitable donor is usually a brother or sister. There is a 1 in 4 chance of a brother or sister being a good match.

It is possible to get a match from a donor who is not a relative. Your doctor will contact one of the registers in the UK to see if there is a suitable donor. This is called a matched unrelated donor (MUD).

Matching donor stem cells

Everyone has their own set of proteins on the surface of their blood cells. The staff in the laboratory compare the surface of your blood cells and the donor blood cells. Your brother or sister are most likely to have similar proteins to you. 

The staff check to see how similar the donor cells are to your own. This test is called HLA typing or tissue typing.

The laboratory staff look for proteins called HLA markers and histocompatibility antigens. They check for 10 HLA markers. The result of this test shows how good the HLA match is between you and the donor.

Mini transplants

These are also called reduced intensity conditioning (RIC) transplants. You have lower doses of chemotherapy than in a traditional stem cell transplant. So the side effects are not generally as bad. 

You might have this treatment if you are not fit or well enough for a traditional transplant. This treatment might not get rid of all your bone marrow cells. So you might have more infusions from your donor after your transplant. These are called donor lymphocyte infusions, they aim to kill any remaining leukaemia cells.

Collecting stem cells

Your donor has injections of growth factors every day for about 4 days before the stem cell collection. Growth factors are natural proteins that make the bone marrow produce more stem cells.

Collecting or harvesting the stem cells takes 3 to 4 hours. Your donor has a drip into each of their arms and these are attached to a machine. Their blood passes out of one drip. It goes through the machine and back into the drip in their other arm. The machine filters the stem cells out of the blood. They are awake for this process.

The stem cells are collected and frozen in preparation for your treatment. Some donors might need to have more stem cells collected the next day.


Transplants are not used as much anymore as targeted cancer drugs have been so successful in treating CML. Research is ongoing, looking into new ways of treating CML. You can search for clinical trials on our trials database. 

If you would like more information about having a stem cell transplant you can call the Cancer Research Nurses on 0808 800 4040. The lines are open 9am to 5pm, Monday to Friday.
Last reviewed: 
23 May 2019
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    Professor J F. Apperley
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