Chronic Myeloid Leukaemia (CML)

What is Chronic Myeloid Leukaemia - Overview

Chronic myeloid leukaemia (CML) is a malignancy of the white cells of the bone marrow and blood. The leukaemia causes a relatively slow but uncontrolled increase in the number of white cells (cells that fight infection) in the bone marrow and blood. This increase can be very marked indeed. There is often an increase in platelets (fragments of cells in the blood that stop bleeding) although there is usually a decrease in the red blood cells causing anaemia. About 60 people will be diagnosed with this type of leukaemia in Victoria each year. It can affect people of any age but is most common between the ages of 50 and 70 years.

What causes CML?

CML occurs when a bone marrow stem cell develops a new but abnormal chromosome called the Philadelphia chromosome (named after the city where it was first discovered. What causes this chromosome to develop in some people is unknown. It does not run in families, and cannot be passed onto children.

What symptoms does CML cause?

CML is often diagnosed on a routine blood test done for other reasons. The uncontrolled increase in white cells can cause non-specific symptoms such as tiredness and lethargy or shortness of breath due to anaemia. Sometimes it can cause fevers, night sweats and loss of weight. The spleen can become enlarged causing fullness or discomfort in the abdomen.

What is the course of CML?

CML potentially can have 3 phases:

1. a chronic phase (where the disease is easy to control with simple medications)
2. an accelerated phase (where the disease becomes more difficult to control) and a
3. blast phase (which is like an acute leukaemia) that is very difficult to control.

In the past, most patients went through these phases unless they underwent a bone marrow transplant. Things are very different nowadays for most patients – largely because of the very clever new drugs that are now available.

What is the prognosis of patients with CML?

Nowadays the prognosis is very good – it is hoped and expected that most patients will be able to live a normal life and have a normal life span. This will probably  require lifelong tablet medication

How is CML diagnosed?

CML is diagnosed by blood test and bone marrow biopsy (a simple procedure where a sample of bone marrow removed from the back or the hip under a local anaesthetic and some light sedation.

The bone marrow biopsy confirms the diagnosis of CML when the Philadelphia chromosome is detected. This chromosome produces a new gene – called bcr-abl – which can be detected by a special molecular test done on the blood.

How is CML treated?

The initial treatment is usually with a simple and very well tolerated chemotherapy tablet called hydroxyurea (Hydrea).

Definitive therapy will be with one of several medications from a class of drugs called tyrosine kinase inhibitors (TKIs) – such as imatinib (Glivec), nilotinib (Tasigna) or dasatinib (Sprycel). These drugs are not chemotherapy drugs but are called small molecule biological drugs – they inhibit the bcr-abl gene of the Philadelphia chromosome which causes the CML cell to die. These drugs are tablets taken by mouth every day for life, and are generally very well tolerated.

With careful management, the great majority of patients will have their CML very well controlled on one of the TKI drugs. Most patients will be able to live and work normally. Just as patients take their blood pressure tablets or cholesterol tablets every day to keep their blood pressure and cholesterol under control, so patients with CML will need to take their TKI tablet every day to keep their CML under control.

Where can I get further information?

The following resources are recommended:

• Leukaemia foundation of Australia CML booklet
• Leukaemia foundation (Ph 1800 620 420)
• Cancer Council Helpline (Ph 13 11 20)