What is CML?
Chronic myeloid leukaemia (CML) is a type of leukaemia that affects developing myeloid cells. CML usually develops slowly during the early stages of disease.
Approximately 50 people are diagnosed with CML each year in New Zealand and can occur at any age but is more common in adults over the age of 40 years old.
In people with CML, the bone marrow produces too many white blood cells called granulocytes. These granulocytes and their immature precursors divide more in the bone marrow and spill out into the bloodstream. They can also expand in the spleen, causing the spleen (and sometimes liver) to increase in size.
CML has 3 important phases:
- Chronic phase - Most people are diagnosed when they are in the chronic phase and may have little or no symptoms.
- Accelerated phase - CML can sometimes change from a relatively stable disease into a more rapidly progressing one. With modern treatments, progression to the accelerated phase of CML is very uncommon.
- Blast phase - CML can transform into a rapidly progressive disease resembling acute leukaemia. Progression to the blast phase is very uncommon thanks to modern treatments.
Signs and symptoms
Most people are diagnosed during the chronic phase of CML and have no or very few symptoms. Initial symptoms may be vague and non-specific, but may become worse over time.
These symptoms include:
- Fatigue
- Weight loss
- Increased sweating
- Abdominal discomfort due to enlarged spleen.
Signs and symptoms of blast phase CML are related to low amounts of normal blood cells in the body which include anaemia, increased risk of infection, bleeding and bruising. It is very uncommon to have accelerated or blast phase CML.
Causes
The cause of CML is not known. We do know that you cannot catch CML from someone else and most people with CML do not have a family/ whānau history of CML.
People with CML have a genetic abnormality in their blood cells called the Philadelphia (Ph) chromosome. The Philadelphia chromosome is formed when part of chromosome 9 breaks off and attaches to part of chromosome 22 in a process called translocation. This chromosomal change is not passed down from parent to child (inherited), it is acquired over time.
There is ongoing research into what the possible causes of this damage might be and what may increase your risk.
Diagnosis
The two main tests for diagnosing CML are a blood test and bone marrow biopsy.
A blood sample is sent to a laboratory (lab) where it is looked at under a microscope.
A bone marrow biopsy is where a sample of your bone marrow is sent to the lab to be looked at under a microscope. The doctor will be able to look at what type of cells are present, the amount of cells being formed, and confirm if there is a Philadelphia chromosome or BCR-ABL gene in the bone marrow cells.
Treatment
Treatment of chronic stage CML aims to control the disease and prevent (or delay) the onset of accelerated or blast phase CML.
Most people with CML will be treated with medications called tyrosine kinase inhibitors (TKIs) or TKI therapy.
If you have a high white blood cell count when diagnosed with CML then you may be given a short course of chemotherapy before commencing TKI therapy.
If you do not respond well to TKI therapy and your CML is getting worse then different treatment will be considered.
