Chronic myeloid leukaemia (CML) risks and causes
This page tells you about chronic myeloid leukaemia and its risk factors. There is information on
How common is CML?
CML is quite a rare condition. The vast majority of cases are in adults. Chronic leukaemia is very rare in children. Leukaemia in children is nearly always acute leukaemia.
Risk factors for CML
The main risk factors for CML are age, gender, radiation, contact with a chemical called benzene and bodyweight. It is most common between ages 40 to 60, and slightly more common in men than women.
If you had radiotherapy for another cancer in the past, this could increase your risk of developing CML. This risk of CML is very small, compared with the risk to your health from the cancer you had.
Contact with a chemical called benzene over many years may also increase CML risk. We know from research that people who are overweight or obese have a higher risk of CML.
Around 7,200 cases of leukaemia diagnosed each year in the UK. Around 3,200 of these are chronic leukaemias, but only about 600 of these are CML. So it is quite a rare condition. Only 1 in every 500 cancers diagnosed is CML.
Although leukaemia is the most common form of childhood cancer, these are nearly all acute leukaemias - chronic leukaemia is very rare in children.
We don't know the cause of most cases of leukaemia but there are some risk factors that may increase your risk. A risk factor is something that may make you more prone to developing a particular condition or disease. For example, smoking is a risk factor for lung cancer and sun exposure is a risk factor for skin cancer.
CML is most common between the ages of 40 and 60. It is slightly more common in men than women.
We know radiation can increase risk to some extent because atomic bomb survivors had an increased risk of leukaemia. And if you have had radiotherapy for another cancer in the past, this could increase your risk of developing CML. Do remember that this risk is very small, compared with the risk to your health of the cancer you need radiotherapy for.
Contact with a chemical called benzene for some years may increase CML risk. Benzene is one of the chemicals in petrol. It is also a solvent used in the rubber industry. Most people wouldn't come into contact with enough benzene for it to be any risk at all.
We mention the Philadelphia chromosome here because people have heard about it. But it isn't really a risk factor. You can't inherit it, or pass it on to your children. It is really a change in a gene that is associated with CML.
Most people with CML are found to have this abnormal chromosome, called the 'Philadelphia chromosome'. It is caused by some of the DNA from one chromosome (no. 9) getting stuck onto another chromosome (no. 22). This is a called a 'translocation', a known type of genetic abnormality. The Philadelphia chromosome causes the cell to make a protein which encourages the leukaemic cells to grow and multiply. It is this chromosome change that causes CML.
Electromagnetic fields are often talked about as a possible risk factor but probably do not increase chronic myeloid leukaemia risk. We are all exposed to electromagnetic radiation. It is all around us. There has been some research that suggested this might be a risk factor for leukaemia. But no increase in risk of CML has ever been found in adults who are exposed to the normal background levels people are exposed to in their own homes.
A combined review of three previously published studies showed that the risk of CML is increased by 26% for people who are overweight or obese, compared to people with a healthy bodyweight.
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