Stem cell transplants for CML
A stem cell transplant may benefit some people with CML.
It’s mainly used to treat people who haven’t responded to treatment with a TK inhibitor. If your doctor thinks a transplant is necessary or possible for you, they will discuss it with you in more detail.
Stem cell transplants are generally only carried out in specialist cancer treatment centres.
A stem cell transplant allows you to have much higher doses of chemotherapy than usual. You may also have radiotherapy (high-energy rays) to the whole body. This can help improve the chances of curing the leukaemia or make a remission last longer.
Stem cells are found inside our bone marrow. They make all the red blood cells, white blood cells and platelets in the blood. Planning a stem cell transplant involves collecting the stem cells from the bloodstream or bone marrow and storing them until they’re needed.
There are two types of stem cell transplant:
allogeneic transplants – when you are given stem cells from someone else (a donor)
autologous transplants (also known as high-dose treatment with stem cell support) – when you are given back your own stem cells.
People with CML are treated using stem cells from a donor. Autologous transplants are only used in CML as part of a research trial.
Stem cells from a donor (allogeneic transplant)
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The aim of this transplant is to give you a source of healthy bone marrow and to try to completely cure the leukaemia.
The most suitable donor is usually a brother or sister who is genetically similar to you, or someone unknown to you (a volunteer unrelated donor) who is a genetic match.
In CML, an allogeneic transplant is usually carried out during the chronic phase when the disease is stable.
A transplant may also be used after the blast phase has been treated and you’re in remission, but it wouldn’t usually be used as treatment for the blast phase.
The first stage of treatment involves having high doses of chemotherapy, sometimes combined with radiotherapy. This destroys your own bone marrow completely.
In some people, especially those who are older or less fit, the high-dose treatment can cause very serious side effects. Sometimes, it’s possible to give lower doses of chemotherapy, which is called reduced intensity conditioning (RIC).
These are called RIC or mini-transplants.
After the chemotherapy (and radiotherapy if used), the donated stem cells are given to you through a drip into your central or PICC line.
The new stem cells, known as the graft, take a few weeks to settle in your bone marrow and start making the blood cells you need. Because you’re very vulnerable to infections during this time, certain precautions will be taken to protect you until your white blood cell count has recovered.
You’ll be looked after in a room on your own and may be given antibiotics to help prevent infections.
The hospital or specialist centre where you are treated will have its own policies on how to care for you during this time.
Your doctor or nurse will discuss this with you beforehand.
Graft versus host disease (GvHD)
When you have an allogeneic transplant, it’s possible that the new cells (the graft) will react against your own tissues (the host). This reaction is called graft versus host disease (GvHD).
Your doctors and nurses will monitor you carefully during the transplant, and for some months afterwards, for any signs of GvHD. If GvHD does occur, it doesn’t mean the transplant has failed. It may even be of benefit, as some of the cells involved in the reaction may also attack any leukaemia cells that may have survived.
You’ll be prescribed drugs to help prevent GvHD and to make it less severe if it occurs.
White blood cells from your donor (donor lymphocyte infusion)
After an allogeneic transplant, your doctors will monitor your blood closely for leukaemia cells. Sometimes, a small number of leukaemia cells remain after an allogeneic transplant.
This may be one of the reasons why CML comes back in some people.
One way of getting rid of these leukaemia cells is to have treatment with a type of white blood cell called lymphocytes. These can also be taken from your donor. The lymphocytes help your immune system to reject the remaining leukaemia cells. This is known as the graft versus leukaemia (GvL) effect. They can be collected from your donor especially for this reason, or they may be taken and stored when the stem cells are originally collected.
The lymphocytes are given through a drip into one of your veins (intravenously). This can be done in the outpatient department. Some people may need to have it done up to three or four times. Sometimes having a donor lymphocyte infusion can cause you to develop graft versus host disease.