About phases of chronic myeloid leukaemia (CML)

Chronic myeloid leukaemia (CML) develops slowly. There are three possible phases of CML:

  • the chronic phase
  • the accelerated phase
  • the blast phase.

Doctors know the phase of CML you are in from:

Most people are diagnosed when CML is in the chronic phase.

Chronic phase

When CML is in the chronic phase, there may be no symptoms and most people lead a normal life. People usually have treatment by taking tablets at home. They have regular blood tests to check how well treatment is working.

For most people, the leukaemia can be well controlled for as long as they continue to take treatment.

In the chronic phase, less than 1 in 10 (10%) of the blood cells in the blood or bone marrow are blast cells.

Accelerated phase

Sometimes CML does not respond very well to treatment. In a small number of people, the leukaemia may progress from the chronic phase to the accelerated phase. Occasionally people may be diagnosed with CML in the accelerated phase.

In this phase, there are more blast cells in the blood or bone marrow. You may also develop symptoms such as:

  • tiredness
  • weight loss
  • bone pain
  • sweating and a high temperature at night.

If you feel unwell or develop new symptoms, let your doctor know.

Blast phase

In some people who have CML in the accelerated phase, the leukaemia may transform into the blast phase. Occasionally people may be diagnosed with CML in the blast phase or progress straight to it from the chronic phase.

The blast phase is like an acute leukaemia. In this phase, more than 2 in 10 (20%) of the blood cells in the blood or bone marrow are blast cells. The blast phase is sometimes called blast crisis.

Relapse

Relapse means the leukaemia cells have come back after a time in remission (where there are no signs of leukaemia cells).

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