Acute myeloid leukaemia risks and causes

Acute myeloid leukaemia is rare. In the UK, around 7,600 people are diagnosed each year with leukaemia. Of those, about 2,300 people have acute myeloid leukaemia. The risk of developing AML increases with age. It is most common in people over 65 years old.

A risk factor is anything that can increase your chance of developing a disease. Different cancers and leukaemias have different risk factors. We don’t know what causes most cases of leukaemia. But there are some factors that may increase your risk of AML.

Remember that having one or more risk factors does not mean that you will definitely get acute myeloid leukaemia. Many people with one or more risk factors never get it. And sometimes people with none of these risk factors develop AML. Risk factors are only a guide to what may increase risk. Some factors may lower the risk of developing leukaemia.

We’ve known for a long time that exposure to very high levels of radiation increases acute leukaemia risk. For example, people exposed to the atomic bomb explosions in Japan at the end of World War 2 have higher rates of leukaemia.

People who have had radiotherapy for cancer have an increased risk of acute leukaemia. Radiotherapy exposes you to a higher than normal level of radiation. But this risk is very small compared to the risk to your health if your original cancer had not been treated.

There is some evidence of an increased risk of childhood leukaemia if the mother is X-rayed during pregnancy. So doctors avoid X-rays for pregnant women wherever possible.

Radon is a naturally occurring radioactive gas. So far, there is no overall evidence that radon increases leukaemia risk. A large French study showed that exposure to radon increased the risk of AML. But an earlier UK study found no increase in leukaemia risk. So we need more research into this.

Exposure to the chemical benzene at work over a long time increases your risk of developing acute leukaemia. There is benzene in traffic pollution but the levels are likely to be too low to affect leukaemia risk. There is also benzene in cigarette smoke (see below).

Smoking cigarettes can increase your risk of developing acute myeloid leukaemia. Researchers estimate that smoking doubles or triples your risk of AML but that the risk quickly drops if you stop smoking. Smoking may account for up to 17 out of 100 (17%) cases of myeloid leukaemia. There is benzene in cigarette smoke and this is likely to be a significant cause.

Certain inherited conditions, such as Fanconi anaemia can increase the risk of developing acute leukaemia. Children with Down’s syndrome are more likely to get acute myeloid leukaemia than other children.

People who have had treatment for Hodgkin’s lymphoma or breast cancer with particular chemotherapy drugs (such as chlorambucil, melphalan or cyclophosphamide) have a slightly increased risk of developing blood changes that can lead to AML many years later. The amount of risk depends on how much treatment you had.

In the 10 years following treatment, survivors of childhood cancer have about 10 times the risk of developing leukaemia than other people. But it is important to remember that this risk is still small compared to the risk to health if the earlier cancer was not treated. The risk also gets lower as time passes since your treatment.

Some types of blood disorder make you more likely to get leukaemia than people without those blood disorders. These include

• Myelodysplastic syndrome
• Myeloproliferative disorders such as polycythaemia rubra vera (PCV) and chronic myeloid leukaemia

Do remember that people with these disorders still only have a small risk of developing AML.

Autoimmune disorders are diseases caused by the body producing an immune response against its own tissues. Research has found that people with particular immune disorders have an increased risk of AML. The conditions include rheumatoid arthritis, autoimmune haemolytic anaemia and ulcerative colitis. The amount that the risk increases ranges from a third to 8 times the risk of a person who does not have these conditions. It is not known whether the increase in risk of AML is due to the autoimmune conditions or the drugs used to treat them.

One study has shown that the risk of AML in the first 18 months of life is more than doubled if the mother drinks alcohol during pregnancy. More studies are needed to confirm this.

You may hear in the news from time to time that some people are worried about power lines and the risk of cancer. Power lines produce high levels of 'low frequency electromagnetic radiation' (EMR).

Although some studies seem to suggest that exposure to very high levels of EMR could increase childhood leukaemia risk, the findings are not very clear. We don’t really know if the childhood leukaemia in these studies was actually caused by low frequency EMR. It could be due to some other common factors, or even chance. Scientists agree that we need more research before we can say for sure one way or the other. Fewer than 1 in 25 UK children are exposed to these high levels. Even if EMR is linked to childhood leukaemia, only 1 in 100 cases (at most) in the UK are likely to be caused by it.

There is more information about electromagnetic radiation in the questions and answers section of CancerHelp UK.

Studies show that very overweight people (with a body mass index of 30 or above) have a slightly higher risk of AML than people who are not overweight.

Many parents worry that vaccination could cause childhood leukaemia, but research shows that this is not likely.