Stages (phases) of 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

International Consensus Classification (ICC) system

The ICC system uses 3 phases to describe CML:

• chronic phase

• accelerated phase

• blast phase

World Health Organization Classification (WHO) system

The WHO system uses 2 phases to describe CML:

• chronic phase

• blast phase

How do doctors work out your phase of CML?

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 white blood cells called blasts. They do a blood test and may do a bone marrow test to find this out.

Your doctors also look at the number of white blood cells and platelets in your blood. And they look at your leukaemia cells to check for changes to chromosomes (abnormalities).

Chronic phase

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 red blood cells (anaemia)
• a higher or lower level of platelets than is normal

Accelerated phase

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 spleen

In accelerated phase CML your blood and bone marrow tests show a higher number of immature (blast) cells than in the chronic phase.

Blast phase

The blast phase is also called the acute phase, blast crisis or blast transformation. This is when the leukaemia transforms into an acute leukaemia . 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.