Chronic myeloid leukaemia (CML)
When your doctors have all your test results, they know how far your chronic myeloid leukaemia (CML) has developed.
In most types of cancer, this is called staging. The stage of your cancer usually describes the size of the cancer and how far it has spread.
CML is slightly different. Instead of stages, doctors use the term phases.
There are 2 systems doctors can use to describe CML. Your doctor might use either the:
International Consensus Classification (ICC) system
World Health Organization Classification (WHO) system
The ICC system uses 3 phases to describe CML:
chronic phase
accelerated phase
blast phase
The WHO system uses 2 phases to describe CML:
chronic phase
blast phase
Different groups of CML experts have slightly different definitions of the 3 phases of CML. We have based our information below on the European LeukaemiaNet definition. This is the definition that researchers use in most of the recent CML clinical trials.
Your doctor looks at all your test results. In particular, they look at the number of immature called blasts. They do a blood test and may do a test to find this out.
Your doctors also look at the number of white blood cells and in your blood. And they look at your leukaemia cells to check for changes to (abnormalities).
The chronic phase is when the leukaemia is most stable and still developing slowly. Most people are in this phase at diagnosis.
Not everyone has symptoms in this phase. If you do have symptoms they might be mild and vague.
In chronic phase CML your blood and bone marrow tests mostly show mature, fully functioning blood cells. You only have occasional immature (blast) cells.
You might also have:
a lower than normal level of (anaemia)
a higher or lower level of platelets than is normal
In the accelerated phase, you have more obvious symptoms. You might notice that you:
feel more tired than usual
have lost weight
have a swollen tummy (abdomen) or have discomfort to the left of your stomach, under your ribs. This is due to an enlarged
In accelerated phase CML your blood and bone marrow tests show a higher number of immature (blast) cells than in the chronic phase.
The blast phase is also called the acute phase, blast crisis or blast transformation. This is when the leukaemia transforms into an . This is usually acute myeloid leukaemia.
You can feel quite unwell and your symptoms could be troublesome. Your spleen is often enlarged.
In blast phase CML many blast cells fill your bone marrow. And there are also more blast cells in your blood.
The leukaemia cells might have spread to other organs.
Last reviewed: 12 Jun 2025
Next review due: 12 Jun 2028
You usually start by seeing your GP if you have symptoms that could be due to CML. Or your GP might arrange to see you if you have had an abnormal blood test result. They will then decide whether to refer you for further tests or to see a specialist.
Targeted cancer drugs called tyrosine kinase inhibitors (TKIs) are the main treatment for CML. Find out more about your treatment options, the different treatments and how they monitor treatment is working.
Survival for chronic myeloid leukaemia (CML) depends on several factors including age. These figures can only give you a general guide about survival for CML.
Chronic myeloid leukaemia (CML) is often a slowly developing condition. Treatment can keep it under control for many years. Find out how to cope and what support is available.
Chronic myeloid leukaemia (CML) is a type of cancer that affects the blood and bone marrow. It usually develops very slowly.
CML starts in the white blood cells called granulocytes. It often develops slowly and treatment can keep it under control for many years. Find out more.
About Cancer generously supported by Dangoor Education since 2010. Learn more about Dangoor Education
What to ask your doctor about clinical trials.
Meet and chat to other cancer people affected by cancer.
Questions about cancer? Call freephone 0808 800 40 40 from 9 to 5 - Monday to Friday. Alternatively, you can email us.
