Stem cell and bone marrow transplant for chronic myeloid leukaemia (CML)

You might have a stem cell or bone marrow transplant as part of your treatment for chronic myeloid leukaemia (CML).

Having a transplant means destroying as many leukaemia cells as possible and replacing these with healthy stem cells .

You first have chemotherapy and other treatments such as radiotherapy. This prepares your body for the healthy stem cells.

After the chemotherapy you have new stem cells into your bloodstream through a drip. These stem cells make their way to the bone marrow . Here they make the blood cells  you need to recover.

You have stem cells or bone marrow from someone else. This is called a donor transplant. 

Why might you have a transplant?

It is uncommon to have a transplant as targeted cancer drugs work well at controlling most people's CML. But your doctor might suggest a transplant if:

• your CML is no longer responding to targeted cancer drugs such as imatinib, nilotinib, dasatinib, ponatinib or asciminib
• you have side effects to your tyrosine kinase inhibitors meaning it is not safe for you to continue with them 
• you have blast phase CML

This type of transplant can cause severe side effects. So it often isn't a treatment option if you are older or have other health problems. 

What are stem cells?

Stem cells are very early cells made in the bone marrow. Bone marrow is a spongy material that fills the bones.

These stem cells develop into 3 different types of blood cells. They are:

• red blood cells - contain haemoglobin and carry oxygen around the body
• white blood cells - part of your immune system and help fight infections
• platelets - help clot the blood and stop bleeding

What’s the difference between a stem cell transplant and a bone marrow transplant?

A stem cell transplant uses stem cells from the bloodstream. This is also called a peripheral blood stem cell transplant (PBSCT). A bone marrow transplant uses stem cells directly from the bone marrow.

Stem cell transplants are the most common type of transplant. Doctors don't often use bone marrow transplants any more. This is because:

• it’s easier to collect stem cells from the bloodstream than bone marrow
• your treatment team can usually collect more cells from the bloodstream
• blood counts tend to recover quicker following a stem cell transplant

In CML, you usually have the stem cells from someone else (a donor). This is known as an allogeneic transplant or allograft.

You might have stem cells from:

• a brother or sister (sibling match)
• a person unrelated to you whose stem cells are similar to yours (matched unrelated donor or MUD)
• cord blood stem cells (umbilical cord)

In some situations, you might have stem cells from a half match - for example, from one of your parents. This is called a haploidentical match.

How do allogeneic transplants work?

Before the transplant you have treatment to prepare your body to receive the stem cells. You might hear this called conditioning treatment. There are two main types of conditioning treatment. These are:

• full intensity (myeloablative) conditioning (MAC)
• reduced intensity conditioning (RIC)

For full intensity conditioning you have very high doses of chemotherapy. With reduced intensity conditioning you have lower doses of chemotherapy. You might also have other treatments such as radiotherapy to the whole body (total body irradiation or TBI ).

Full intensity conditioning kills all the leukaemia cells and healthy cells in your bone marrow. Reduced intensity conditioning with lower doses means that some leukaemia cells and healthy cells are left behind. Both types of conditioning make space in your bone marrow for the donor stem cells and dampen down your immune system. This prepares your body for your transplant so it doesn’t reject the donor cells.

After the conditioning treatment you have the donor stem cells into your bloodstream through a drip. The cells find their way to your bone marrow. Your body then starts making blood cells again and your bone marrow slowly recovers.

Recovering from your transplant

Your donor stem cells find their way into your bone marrow where they make the blood cells you need. It takes a while for your bone marrow to start making blood cells again and for your blood counts to come up. Your doctors call this engraftment. Engraftment can take between about 2 to 3 weeks, but it can take longer. 

You have regular blood tests to check when your bone marrow starts to make new blood cells.

While you recover you continue to have treatment for any side effects and symptoms. This might include:

• antibiotics and antiviral medicines to treat and prevent infection
• platelet transfusions if the number of platelets in your blood is low
• blood transfusions if your red blood cells are low
• medicines to relieve a sore mouth, diarrhoea and sickness
• medicines to dampen down your immune system

One of the main problems with waiting for your blood counts to come up is that you’re at a very high risk of developing an infection. For this reason, you stay in hospital in a room on your own until your blood counts are high enough for you to go home. 

Your room usually has special air filters. These filters trap bacteria that might be in the air that could cause infection. Anyone who enters your room will have to follow strict infection control procedures.

Your healthcare team might refer to this as being in isolation. Your team will monitor you closely and come into your room regularly. They just take special precautions when they come into your room. It doesn’t mean you can’t have visitors, but they may suggest limiting them to one or two each day. If your visitors are unwell they won’t be allowed to see you. They should also stay away if they have been in contact with someone who has an infectious illness.

Your nurse may suggest that family and friends contact you before visiting to make sure you feel up to it. 

You might have to follow a special diet including foods that are unlikely to give you an infection. 

Side effects of a stem cell transplant

There are other possible side effects of having a transplant. Not everyone will get them and the severity of each side effect will vary from person to person. You usually start to feel better as your blood counts recover. Some of the other possible side effects include:

• breathlessness and looking pale due to a drop in the red blood cells
• increased risk of bleeding
• feeling or being sick
• tiredness and lacking energy
• hair thinning or loss
• sore mouth and ulcers
• diarrhoea

Graft versus host disease (GvHD)

If you have had a transplant from a donor, you are at risk of GvHD. This is because the stem cells contain immune cells from the donor. These cells can sometimes attack some of your own body cells. Symptoms of GvHD include:

• diarrhoea
• weight loss
• yellowing of the whites of the eyes and skin (jaundice)
• skin rashes
• shortness of breath

Let your nurse or doctor know if you have any of these symptoms.

Loss of fertility

You are at higher risk of not being able to get pregnant or get someone else pregnant after having a stem cell transplant for CML. Talk to your doctor before starting treatment if this is a concern for you. They could explain how this could affect you.