Leukaemia - myeloid, chronic

About chronic myeloid leukaemia

The term leukaemia refers to a group of cancers of the white blood cells and bone marrow. Bone marrow produces white blood cells, of which there are two types – lymphocytes and myeloid cells. Myeloid cells are responsible for producing many other types of blood cell, including red blood cells, platelets and a type of white blood cell called granulocytes. Usually these granulocytes divide in a controlled way but if you have leukaemia, they start to divide and grow in an uncontrolled way and, in the more advanced stages of the condition, they don’t develop properly. Because it affects the granulocytes, CML is also sometimes called chronic granulocytic leukaemia.

Leukaemia is described as acute (growing rapidly) or chronic (growing slowly). Chronic leukaemia is divided into two main types – CML and chronic lymphocytic leukaemia (CLL). This factsheet focuses on CML.

In CML, the granulocytes that are dividing rapidly start to fill up your bone marrow and eventually prevent it from producing enough healthy blood cells. In the early stages, your blood cells may still work almost as well as usual. However, if you don’t get effective treatment, the condition may progress and lead to more severe symptoms.

About 600 people in the UK are diagnosed with CML each year. The risk of developing the condition increases as you get older but it’s still the least common type of leukaemia. It's very rare in children.

Symptoms of chronic myeloid leukaemia

Many people don’t have any symptoms and CML is only picked up when they have a blood test for something else. If you do have symptoms, they may include:

  • tiredness and breathlessness
  • weight loss and decreased appetite
  • fever
  • sweating more than usual, especially at night
  • headaches and vision problems
  • discomfort in your abdomen (tummy) caused by your spleen being enlarged
  • bleeding or bruising more easily than usual
  • itching

Many of these symptoms are similar to those of other conditions so it’s easy to confuse them. Although these symptoms aren’t always caused by CML if you have them, see your GP.

Causes of chronic myeloid leukaemia

Most people develop CML because an abnormality develops in a chromosome – this is called the Philadelphia chromosome. Chromosomes are structures that contain genes – you inherit these from your parents and they determine everything about you. The Philadelphia chromosome carries an abnormal gene called BCR-ABL, which you develop by chance at some point during your life.

Some things that may increase your risk of developing the Philadelphia chromosome, and hence CML, include:

  • exposure to radiation
  • increasing age
  • being male – you’re slightly more likely to develop CML if you’re a man
  • a weakened immune system – if you have HIV/AIDS, or you’re taking medicines that suppress the immune system, such as chemotherapy medicines
  • being overweight – if you have a body mass index (BMI) of 30 or above, you’re slightly more likely to develop CML

For more information about the Philadelphia chromosome, see our frequently asked questions.

Diagnosis of chronic myeloid leukaemia

Your GP will ask about your symptoms and examine you and may ask you to have a blood test to check the levels of different cells in your blood. If your GP thinks that you may have CML, he or she will refer you to a specialist called a haematologist (a doctor who specialises in conditions of the blood).

Your haematologist will carry out some further investigations to confirm whether or not you have CML. These tests may include:

  • further blood tests
  • a physical examination to check whether your spleen is enlarged

If these suggest that you have CML, you may have one or more of the following tests to see how far your leukaemia has progressed and which treatment will be best for you. These may include:

  • a bone marrow biopsy – your doctor will use a needle to remove a sample of your bone marrow which is then examined under a microscope
  • tests on the chromosomes in your bone marrow cells to see if you have the Philadelphia chromosome
  • tests to see if you have the BCR-ABL gene – this is a very sensitive test
  • an ultrasound scan to check if you have an enlarged spleen

Phases of CML

You may hear your doctors referring to different phases of CML. These identify how far your leukaemia has progressed so that you receive the most appropriate treatment.

There are three phases of CML.

  • The chronic phase – about nine out of 10 people with CML are in this phase when they are first diagnosed. You may not have any symptoms but if you do, they are likely to be mild.
  • The accelerated phase – this is when your symptoms become more severe, including losing weight, bruising and having abdominal pain or discomfort. This is because there are more undeveloped cells in your blood and bone marrow.
  • The blast phase – this is when the condition develops into an aggressive form of leukaemia and your cells grow rapidly. You’re likely to have severe symptoms, including an enlarged spleen.

Treatment of chronic myeloid leukaemia

Your treatment will depend on the stage of CML and on your general health. You may have a combination of different therapies. If your condition is in the chronic phase, your treatment will be aimed at controlling your symptoms and preventing CML from progressing for as long as possible. If you have accelerated or blast phase CML, your treatment will try to reduce your symptoms and, if possible, cure your condition.


Your doctor will usually prescribe you a medicine called imatinib to take, or a newer alternative called nilotinib. These are both tyrosine kinase inhibitors. They work by blocking the signals that make the cancer cells grow and multiply, and can get rid of the Philadelphia chromosome from your blood and bone marrow.

You take both of these medicines by mouth and most people don’t get many serious side-effects. In many people with CML, these medicines can keep the condition under control for many years.

Imatinib and nilotinib can be used to control chronic and accelerated phase CML. You can also take imatinib if you have blast stage CML, as long as you haven’t taken it before. You can continue taking both of these medicines for as long as they are controlling the condition. Your doctor will monitor you carefully, taking blood tests to check you’re still in remission. If your cancer is in remission, your signs and symptoms of the condition have decreased or disappeared.

If imatinib or nilotinib haven’t worked for you or if you’re having severe side-effects, your doctor may suggest taking a newer, alternative tyrosine kinase inhibitor called dasatinib.

Interferon alpha is another medicine that is used occasionally to treat CML in the chronic stage. It can be combined with chemotherapy. You have this medicine as injections once a day and side-effects vary greatly from person to person.


You may need to have chemotherapy if you haven’t responded to other treatment. Chemotherapy uses medicines to destroy the leukaemia cells in your bone marrow. A chemotherapy medicine called hydroxycarbamide is usually given to you as tablets. Hydroxycarbamide can fully control chronic phase CML and most people have very few side-effects, but it can’t get rid of the Philadelphia chromosome and therefore can’t prevent chronic CML from progressing to the accelerated or blast phases.

If you have accelerated or blast phase CML, you may need to have high-dose chemotherapy. This may involve a combination of medicines that are given to you through a drip into a vein, usually in your arm.

Bone marrow or stem cell transplant

If you haven’t responded well to other treatments, your doctor may suggest that you have a bone marrow (stem cell) transplant (preferably from a brother or sister) into your body. This is a very intensive type of treatment as it involves killing all your bone marrow cells as well as the leukaemia ones. Therefore, you need to be in general good health to have a transplant.

New treatments

Many possible new treatments for CML are being tested in clinical trials all the time. These include new chemotherapy medicines and biological therapies, as well as different types of transplants. Research is also being carried out on vaccines for CML. You may be able to take part in a clinical trial to test one of these new treatments – speak to your doctor for more information.

Will I need to go into hospital for chemotherapy for chronic myeloid leukaemia?


Most people don't need to but it depends on the type of chemotherapy you're having.


It’s likely that if you’re having chemotherapy for CML, you will be able to take the medicine as tablets and you can do this at home (see chemotherapy at home, for more information). If you’re having chemotherapy as injections via a drip, you will probably need to go into hospital for them.

If you’re having chemotherapy as part of a bone marrow or stem cell transplant, you will need to go into hospital, usually for several weeks. This is because the chemotherapy is very intensive and you will need specialised care.

Ask your doctor or nurse for more information about your treatment.

How does someone get the Philadelphia chromosome?


The Philadelphia chromosome occurs by chance and can develop at any point during your life. It can't be passed on to you by your parents.


Your body is constantly producing new cells to replace existing ones. To do this, cells produce copies of themselves and the chromosomes they contain. Chromosomes contain genes, which control how your body works.

Bits of chromosomes occasionally break off and attach to other chromosomes, but this doesn't always have an effect on your body and it may go unnoticed. If you have the Philadelphia chromosome, one chromosome has accidentally moved a section of itself to another, forming a gene called BCR-ABL. This gene causes the cells in your bone marrow to start growing abnormally.

Having the Philadelphia chromosome is the main reason why people go on to develop CML. A small number of people who have this chromosome can also go on to develop acute lymphoblastic leukaemia.

What is involved in becoming a bone marrow donor?


If you wish to be considered as a bone marrow donor, you will need to sign up to the British Bone Marrow Registry by registering with the National Blood Transfusion Service or the Anthony Nolan Trust.


To become a donor, you must be aged between 18 and 49. When you have been registered, you will need to give a sample of blood, which is held on file. If you match someone who needs bone marrow or stem cells, you will be contacted by the service.

There are two ways that you can donate bone marrow if you’re found to match someone who needs a transplant. Usually stem cells will be taken from your blood using a machine that separates them from the rest of your blood. Alternatively, stem cells can be removed from the bone marrow in your hip bone. You will need to have a general anaesthetic for this procedure and stay in hospital for a couple of days afterwards.

Can I take time off work as sick leave to be treated for chronic myeloid leukaemia?


You will need to check with your employer about what sick pay you’re entitled to if you need to take time off work for treatment.


How much sick leave you can take for treatment depends on the type of work you do and the terms of your contract with your employer. Your employer may run a sick pay scheme or you may get statutory sick pay so you can take time off and still be paid when you go for your treatment. Ask your manager if there is a scheme where you work and whether you’re entitled to this.

It’s possible that you will only need to take oral medicines (tablets) for CML and these often have no serious side-effects. You may be able to carry on working as usual with only occasional time off for hospital visits.