Acute lymphoblastic leukemia (ALL) is the most common type of leukemia (cancer of the blood and bone marrow) in children and can also occur in adults.
Acute lymphocytic leukemia occurs when a bone marrow cell develops changes (mutations) in its genetic material or DNA. A cell’s DNA contains the instructions that tell a cell what to do. Normally, the DNA tells the cell to grow at a set rate and to die at a set time. In acute lymphocytic leukemia, the mutations tell the bone marrow cell to continue growing and dividing.
When this happens, blood cell production becomes out of control. The bone marrow produces immature cells that develop into leukemic white blood cells called lymphoblasts. These abnormal cells are unable to function properly, and they can build up and crowd out healthy cells.
It’s not clear what causes the DNA mutations that can lead to acute lymphocytic leukemia, but it is thought to be the result of a combination of genetic and environmental factors. Some known risk factors for ALL include:
Genetic conditions
Certain rare, inherited conditions can increase the risk of acute leukaemia, including:
- Down’s syndrome
- Fanconi anaemia
- ataxia telangiectasia
- Bloom syndrome
Previous treatment with chemotherapy
People who have had certain chemotherapy drugs in the past have a slightly increased risk of developing leukaemia some years later. The risk depends on how much treatment you had. Some of the drugs include:
- etoposide with cisplatin and bleomycin
- thiotepa
- busulfan
- chlorambucil
It’s important to remember that this risk is still very small compared to the risk to your health if the cancer had not been treated.
Ionising radiation exposure
High energy (ionising) radiation can cause cancer because it can affect your cells and damage the DNA. We know that exposure to very high levels of ionising radiation increases acute leukaemia risk. For example, people exposed to the atomic bomb explosions in Japan at the end of World War 2 had a higher risk of developing leukaemia.
A 20 year study has followed up workers who helped clean up after the Chernobyl nuclear power plant accident in 1986. It shows that even at low doses of ionising radiation there is an increased risk of all types of leukaemia.
Some chemotherapy and radiation treatments used to treat other cancers can also increase the risk of developing ALL. CT scans and radiotherapy treatment also use ionising radiation. Research suggested that this could increase the risk of children developing leukaemia later in life. However, it’s important to note that doctors make sure the benefits of having the test or treatment outweighs the risks.
Exposure to certain chemicals
Some studies have suggested that exposure to certain chemicals, such as benzene at work can increase the risk of developing ALL. Exposure to benzene may occur in:
- petrol industry
- chemical industry
- pharmaceutical industry
- rubber industry
- shoe production
- printing industry
The higher the level of exposure over many years, the greater the risk. Another study showed that you have an increased risk of developing ALL if your parents were exposed to benzene before and during pregnancy.
Weakened immunity
A study looked at published research into people:
- with HIV or AIDS
- treated with medicines that lower immunity after an organ transplant
The researchers found that these people have a risk of leukaemia that is up to 3 times higher than people without these factors.
It’s important to note that most people with these risk factors do not develop ALL, and many people with ALL do not have any known risk factors.