Phases of chronic myeloid leukaemia

The chronic phase Back to top

Most people are diagnosed when the CML is in the chronic phase. At this time CML develops very slowly and is often stable for a long time. It’s sometimes called the ‘stable phase’. There may be no symptoms and most people lead a normal life.

It’s rare to need to go into hospital. You can have treatment| as an outpatient. This doesn’t usually cause many side effects. You’ll have regular blood tests to check how well you are responding to treatment.

Most people who start treatment in the chronic phase have their leukaemia well-controlled without any symptoms. And, if they keep taking their treatment, the leukaemia can be kept under control for years, perhaps even decades.

In some people CML doesn’t respond as well to treatment. And, in a few people, the leukaemia may progress from the chronic phase to a more advanced phase of the disease within about five years of diagnosis.

The accelerated phase Back to top

In a small number of people, the leukaemia may gradually move into an accelerated phase. In this phase there are more immature cells (known as blasts) in the blood and bone marrow and the leukaemia develops more quickly. Sometimes this change may be picked up from your blood tests, in which blasts can be seen. Or, it may come to light because you develop new symptoms. If you feel less well or develop new symptoms, let your doctor know straight away.

The treatment| for the accelerated phase is often more intensive than in the chronic phase and you may need to spend some time in hospital as an inpatient.

The blast phase Back to top

After some time, usually months, in the accelerated phase, the leukaemia ‘transforms’ into a blast phase, which is more like an acute leukaemia. In this phase there are many immature cells (blasts) filling much of the bone marrow. There are also many more blasts found in the blood than normal.

In some people, who have CML that doesn’t respond to treatment, the leukaemia changes quickly from the chronic to the blast phase without going through the accelerated phase.

Myelofibrosis

Rarely, CML causes scar tissue to form (fibrosis) inside the bone marrow. This condition is called myelofibrosis. Areas of the bone marrow that are affected by scarring don’t work properly and can’t make new blood cells. Because of this, people with myelofibrosis may need regular transfusions of blood and platelets.

We have more information on myelofibrosis|, as well as information on blood| and platelet transfusions|. 

Remission Back to top

Remission is when the blood and bone marrow go back to normal following treatment. There are different levels of remission.

Relapse Back to top

Relapse means that leukaemia cells have reappeared after a period of remission.