What is CML?1,2

CML is a type of blood cancer that originates in the bone marrow. It develops slowly and typically affects those over the age of 60. CML causes the bone marrow to go into overdrive, producing too many white blood cells that are abnormal. These white blood cells are not fully developed and cannot fight infections as well as normal white blood cells.

Although impaired, the abnormal white blood cells still have some ability to fight infections and because of this, people with CML can live for a long time without symptoms. However, if left untreated, CML may become more aggressive and can severely compromise the body’s immune system.


What causes CML?1,2

CML is caused by a chromosomal change, where two sections of DNA on different chromosomes switch places. This is known as the Philadelphia chromosome. It is not understood why this happens, but it occurs spontaneously during life and cannot be passed on to children. Chromosomes are clusters of genes, so the formation of the Philadelphia chromosome results in a fusion gene being produced. This fusion gene causes the cellular machinery that produces white blood cells to become overactive, which causes CML.


What are the symptoms of CML?1

CML develops slowly and in early stages may not cause any symptoms. CML may only be picked up during tests carried out for another reason.

As the CML develops, symptoms can include:

  • Tiredness
  • Weight loss
  • Night sweats
  • Tenderness and swelling in the left side of the tummy
  • Feeling full after small meals
  • Pale skin and shortness of breath
  • Fever
  • Bruising and bleeding easily
  • Frequent infections
  • Bone pain


How is CML diagnosed?3,4

CML is usually diagnosed by a haematologist after some tests.

Tests used to confirm a diagnosis of CML include:

  • A blood test to identify large numbers of abnormal white blood cells
  • A biopsy of the bone marrow to confirm the CML diagnosis
  • A genetic test to detect the Philadelphia chromosome or fusion gene


What is the goal of treatment for CML?5,6

CML can usually be managed with treatments and most people with chronic phase CML have a normal life expectancy. Treatments for CML work by reducing the production of abnormal white blood cells to slow disease progression. At all times the goal of treatment is to keep the CML stable (in chronic phase) for as long as possible or even into remission (the absence of active disease). If a patient is in remission for several years they may be able to discontinue treatment and instead be monitored regularly to make sure the cancer remains controlled. This is known as treatment-free remission. This will be done under full consultation with their clinician.




  1. NHS. Chronic myeloid leukaemia. Overview. Available at: https://www.nhs.uk/conditions/chronic-myeloid-leukaemia/. Last accessed May 2020.
  2. Blood cancer UK. What is chronic myeloid leukaemia. Available at: https://bloodcancer.org.uk/understanding-blood-cancer/leukaemia/chronic-myeloid-leukaemia/what-is-cml/. Last accessed May 2020.
  3. NHS. Chronic myeloid leukaemia. Diagnosis. Available at: https://www.nhs.uk/conditions/chronic-myeloid-leukaemia/diagnosis/. Last accessed May 2020.
  4. Blood cancer UK. Symptoms and diagnosis of chronic myeloid leukaemia. Available at: https://bloodcancer.org.uk/understanding-blood-cancer/leukaemia/chronic-myeloid-leukaemia/cml-symptoms-diagnosis/cml-tests/. Last accessed May 2020.
  5. NHS. Chronic myeloid leukaemia. Treatment. Available at: https://www.nhs.uk/conditions/chronic-myeloid-leukaemia/treatment/. Last accessed May 2020.
  6. Hochhaus A, et al. Leukemia. 2020;34:966–984. 
Rate this content: 
No votes yet
ONC20-C059 June 2020.

Ask Speakers


Medical Information Request

Reporting of side effects
If you get any side effects, talk to your doctor, pharmacist or nurse. This includes any possible side effects not listed in the package leaflet. You should also report side effects directly via the Yellow Card Scheme at yellowcard.mhra.gov.uk.
By reporting side effects you can help provide more information on the safety of this medicine.