Chronic myeloid leukaemia (CML) can be present for some time before a person realises anything is wrong. A routine blood test may reveal an unusually high white blood cell count, even without clear symptoms. For others, persistent tiredness, night sweats or unexplained weight loss may lead them to seek medical advice.

Once CML is diagnosed, doctors look at how far the condition has progressed. This helps them understand how the abnormal cells are behaving and choose an appropriate treatment. CML is traditionally divided into three phases: chronic, accelerated and blast phase. Each describes a different pattern of disease activity.

Key Takeaways

  • CML progresses through three traditional phases: chronic, accelerated and blast.
  • The chronic phase usually progresses slowly and often causes few symptoms.
  • The accelerated phase involves increasing disease activity and changes in blood cell production.
  • The blast phase is the most advanced stage, with a rapid increase in immature blood cells.
  • Imatinib and regular blood and molecular tests help manage CML and monitor treatment response.

Chronic Phase: The Earliest Stage

The chronic phase is the most common phase at diagnosis. At this point, the bone marrow produces too many abnormal white blood cells, but the disease usually progresses more slowly than in the later phases.

Many people have few symptoms, particularly when CML is discovered through routine testing. Others may notice tiredness, night sweats, or discomfort under the left ribs if the spleen enlarges. These symptoms could be easy to overlook because they may develop gradually.

Blood tests help doctors understand what is happening. The white blood cell count may be raised, and further testing can identify the BCR::ABL1 genetic abnormality associated with CML. In the traditional classification, blast cells make up less than 10% of blood or bone marrow cells during this phase.

Treatment during the chronic phase aims to keep the abnormal cells under control. Many people respond well to treatment and continue living with CML in this phase for years, provided their condition is monitored and their treatment remains effective.

Accelerated Phase: When the Disease Changes

CML can become harder to control as the number of abnormal cells rises. During the accelerated phase, the bone marrow may struggle to produce healthy blood cells in the usual proportions.

The changes can show up in everyday life, too. Someone who had few symptoms at diagnosis might start feeling unusually tired, develop a fever, or experience bone pain. Blood tests may reveal further changes, especially when treatment no longer produces the expected response.

Doctors traditionally identify this phase when blast cells account for 10% to 19% of cells in the blood or bone marrow. They also look at chromosome abnormalities, blood counts and the patient's response to treatment. No single result tells the whole story, so these findings need to be considered together.

If the results suggest that CML is progressing, the treating team may need to reconsider the existing treatment plan. The decision depends on the test results and the person's medical history.

Blast Phase: The Most Advanced Stage

In the blast phase, immature blood cells begin multiplying much more aggressively. These cells can take up space in the bone marrow that would otherwise be used to produce healthy blood cells.

The effects may become more noticeable as normal blood production declines. A shortage of red blood cells can worsen fatigue and weakness, while low levels of healthy white blood cells or platelets may leave a person more vulnerable to infections or bleeding. As CML progresses, fever, bone pain, or discomfort from an enlarged spleen can occur. Another change doctors look for is an increase in blasts, the immature blood cells that have not developed fully.

When these cells account for 20% or more of the cells in the blood or bone marrow, the condition meets the traditional definition of blast phase. At this stage, the bone marrow may struggle to produce enough healthy blood cells. The treatment approach depends on the person's condition, previous treatment and the results of their latest investigations.

Treatment and Regular Monitoring

For someone living with CML, a blood test can reveal changes that are not obvious from how they feel. This is why follow-up continues even when symptoms have settled. Doctors use blood counts and molecular tests to check how the condition is responding.

Imatinib targets the abnormal BCR::ABL1 protein that causes affected cells to multiply. As treatment begins to work, the number of these cells may fall. Molecular test results help show whether this reduction is happening, alongside changes seen in routine blood counts.

If you have been prescribed an Imanib tablet, confirm the product and strength with your doctor or pharmacist and take it according to your prescription. If you experience side effects or feel that your treatment is not suiting you, speak to your healthcare team. Do not alter the dose or stop taking it on your own.

Feeling well does not always mean that CML is fully controlled. Abnormal cells may still be present even after symptoms improve, which is why keeping up with scheduled tests matters. Your doctor can use these results to decide whether the current treatment continues to meet your needs.

Conclusion

CML can change over time, and its phase helps doctors understand what those changes mean for treatment. Blood counts and molecular tests provide information that symptoms alone cannot offer. Staying in touch with your healthcare team and attending follow-up appointments remain important throughout care.


Disclaimer: This article is for general information only and should not replace advice from a qualified healthcare professional. Speak to your doctor about CML diagnosis and treatment. Do not stop or change a prescribed medicine without medical guidance.