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Chronic myeloid leukaemia (CML)

Leukaemia is the name given to a group of cancers of the white blood cells and bone marrow. There are different types of leukaemia, and it can be acute (grows rapidly) or chronic (grows slowly).

We’ve put together information here about chronic myeloid leukaemia (CML). This sort affects a type of white blood cell called myeloid cells. Most people don't have any symptoms with CML but it can make you feel tired and weak. It may be possible to cure CML with some treatments.

If you have any type of leukaemia, you produce abnormal white blood cells. They build up in your bone marrow and prevent the production of other healthy blood cells. There are two main types of white blood cells – lymphocytes and myeloid cells – and CML affects myeloid cells. It’s described as chronic because it grows slowly.

In the early stages of CML, your blood cells may still work almost as well as usual. However, if you don’t get treatment, the condition is likely to get worse and lead to more severe symptoms.

About one to two people in every 100,000 in the UK are diagnosed with CML each year. You can get CML at any age but it’s not common in children under 10. Your risk of developing the condition increases you get older and it’s most common in people aged about 50 to 60.

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  • Symptoms Symptoms of chronic myeloid leukaemia

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

    • feeling very tired and weak
    • feeling short of breath
    • losing weight for no reason you can think of, and losing your appetite
    • problems with your vision
    • discomfort in your abdomen (tummy) 
    • a fever
    • sweating more than usual – especially at night
    • bruising more easily than usual or bleeding (such as nosebleeds)

    If you have these symptoms, contact your GP.

  • Diagnosis Diagnosis of chronic myeloid leukaemia

    Your GP will start off by asking about your symptoms and may ask to examine you. They may also ask about your medical history. 

    Your GP may ask you to have a blood test to check the levels of different cells in your blood. If the results suggest you have CML, you’ll be referred to a haematologist. This is a doctor who specialises in conditions that affect the blood.

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

    • further blood tests
    • a physical examination to check whether your spleen is enlarged (this can mean your body is producing more white blood cells than usual)

    If the results of these suggest that you have CML, you may have one or more tests to see how far it’s progressed. These will also help to decide which treatment is best for you. The tests may include:

    • a bone marrow biopsy – your doctor will use a needle to remove a sample of your bone marrow which is examined under a microscope
    • tests on chromosomes in bone marrow cells to see if you have the Philadelphia chromosome (see Causes for more information)
    • tests to see if you have an abnormal gene called the BCR-ABL gene (see Causes for more information)
    • an ultrasound scan to check if you have an enlarged spleen

    Phases of CML

    You may hear your doctors talking about different phases of CML. These identify how far your leukaemia has progressed so that you receive the right 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 because there are more abnormal cells in your blood and bone marrow.
    • The blast phase – this is when the condition develops into a severe form of leukaemia and your cells grow rapidly. It’s likely that your symptoms will be worse and your spleen will be enlarged.
  • Treatment Treatment of chronic myeloid leukaemia

    Your treatment will depend on what stage of CML you have, and your general health. You may have a combination of different therapies. If you have chronic phase CML, your treatment will aim to control your symptoms and prevent CML from progressing for as long as possible. If you have accelerated or blast phase CML, your treatment will try to reduce or stop your symptoms. If your symptoms stop, it’s called remission and this can last for years. It may be possible to cure CML with some treatments.


    Your doctor may prescribe you a type of medicine called a tyrosine kinase inhibitor to treat CML. These work by blocking the signals that make cancer cells grow and multiply. Examples of these types of medicine are imatinib and nilotinib. You take both of these medicines as tablets and most people don’t get many serious side-effects. Sometimes these medicines can keep CML under control for years.

    Imatinib and nilotinib are used to control both the chronic and the 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 carry on taking both of these medicines for as long as they are controlling your condition. Your doctor will keep a careful watch on you, taking regular blood tests to check you’re still in remission.

    If imatinib or nilotinib don’t work for you or you get severe side-effects, your doctor may suggest taking an alternative tyrosine kinase inhibitor called dasatinib.


    You may need to have chemotherapy if tyrosine kinase inhibitors haven't worked for you. Chemotherapy uses medicines to destroy the leukaemia cells in your bone marrow.

    One type of chemotherapy medicine is called hydroxycarbamide and you usually take this as tablets. Hydroxycarbamide can treat the chronic phase CML and you’ll probably have very few side-effects. However, it can’t prevent chronic CML from progressing to the accelerated or blast phases.

    If you have blast phase CML, you may need to have a combination of chemotherapy medicines. These will be 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 with high-dose chemotherapy. This is a very intensive type of treatment as it involves killing all your healthy bone marrow cells as well as the leukaemia ones. Therefore, you need to be in general good health to have this treatment. The cells need to come from a suitable donor – preferably a brother or sister if you have one.

    New treatments

    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 done into vaccines for CML. You may be able to take part in a clinical trial to test one of these new treatments – ask your doctor for more information.

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  • Causes Causes of chronic myeloid leukaemia

    Most people develop CML because they have an abnormal chromosome 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 don't inherit and can't pass on to your children. You develop it by chance at some point during your life.

    Some things that may trigger the Philadelphia chromosome to develop, and therefore CML, include:

    • exposure to radiation
    • getting older
    • your gender – men are slightly more likely to develop CML than women
    • exposure to a chemical called benzene, although it's not known for sure if this is a trigger yet

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

  • FAQs FAQs

    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 can take the medicine as tablets at home. For more information, see our topic about having chemotherapy at home. If you’re having chemotherapy as injections through a drip, you may 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. This is cancer that grows more rapidly than CML.

    How can I donate bone marrow?


    You can sign up to the British Bone Marrow Registry by registering with the National Blood Transfusion Service or the charity Anthony Nolan.


    You must be aged between 18 and 30 to register as a donor (although you can stay listed as a donor until you're 60). Once you have 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, the service will get in touch with you.

    There are two ways that you can donate bone marrow if you’re found to match someone who needs a transplant. The most common is to have stem cells 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’ll need to have a general anaesthetic for this procedure and stay in hospital for a couple of days.

    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.


    It’s possible that you will only need to take 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.

    If you do need to have time off, how much sick leave you can take depends on the type of work you do. It will also depend on 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.

  • Resources Resources

    Further information


    • Overview of leukemia. The Merck Manuals., published July 2012
    • Leukemias. Medscape., published 1 April 2014
    • Chronic leukemia. The Merck Manuals., published July 2012
    • Chronic myelogenous leukemia. Medscape., published 22 August 2014
    • Chronic myeloid leukaemia. PatientPlus., published 19 July 2012
    • NCCN guidelines for patients: chronic myelogenous leukaemia. National Comprehensive Cancer Network., published 2014
    • Bosutinib for previously treated chronic myeloid leukaemia. National Institute for Health and Care Excellence (NICE), November 2013.
    • Chronic myelogenous leukaemia. BMJ Best Practice., published 1 November 2013
    • Dasatinib, nilotinib and standard-dose imatinib for the first-line treatment of chronic myeloid leukaemia (part review of technology appraisal guidance 70). National Institute for Health and Care Excellence (NICE), April 2012.
    • Baccarani M, Pileri S, Steegmann JL, et al. Chronic myeloid leukemia: ESMO clinical practice guidelines for diagnosis, treatment and follow-up. Ann Oncol 2012; 23(7):vii72–7. doi:10.1093/annonc/mds228
    • Joint Formulary Committee. British National Formulary (online) London: BMJ Group and Pharmaceutical Press., accessed 27 October 2014
    • About chemotherapy for chronic myeloid leukaemia (CML). Cancer Research UK., published 29 April 2013
    • Chronic myelogenous leukemia treatment. National Cancer Institute., published 21 October 2014
    • Chronic myeloid leukaemia (CML) research. Cancer Research UK., published 29 November 2013
    • General information about chronic myelogenous leukemia. National Cancer Institute., published 11 November 2014
    • Bone marrow and stem cell transplants for chronic myeloid leukaemia (CML). Cancer Research UK., published 29 April 2013
    • General information about adult acute lymphoblastic leukemia (ALL). National Cancer Institute., published 21 February 2014
    • Q&A. NHS Blood and Transplant., published 21 October 2014
    • Who can join the register? Anthony Nolan., accessed 1 December 2014
    • Government benefits. Cancer Research UK., published 15 October 2014
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