CCS is actively monitoring and responding to the recommendations of the Public Health Agency of Canada regarding coronavirus disease (COVID-19).
Risk factors for childhood leukemia
A risk factor is something that increases the risk of developing cancer. It could be a behaviour, substance or condition. Most cancers are the result of many risk factors. But sometimes childhood leukemia develops in children who don’t have any of the risk factors described below.
Childhood leukemia is most common among Caucasian and Hispanic children. About 75% of all childhood leukemias are acute lymphoblastic leukemia (ALL), and most of these ALLs occur in children between the ages of 1 and 4 years. More boys than girls develop ALL. About 20% of all childhood leukemias are acute myelogenous leukemia (AML).
The following are risk factors for childhood leukemia. Most of the known risk factors are not modifiable. This means that you can’t change them. Until we learn more about these risk factors, there are no specific ways you can reduce the risk.
Risk factors are generally listed in order from most to least important. But in most cases, it is impossible to rank them with absolute certainty.
Known risk factors
There is convincing evidence that the following factors increase your risk for childhood leukemia.
Genetic syndromes are diseases or disorders caused by a change (mutation) in one or more genes. The following genetic syndromes can increase the risk of developing childhood leukemia.
Down syndrome is linked with intellectual disability, a characteristic facial appearance and poor muscle tone. Children with Down syndrome may be born with a variety of birth defects. They have a higher risk of developing several medical conditions, including certain types of cancer (such as leukemia).
Bloom syndrome is caused by a large number of abnormal chromosomes. Children with Bloom syndrome are usually smaller than average, have a high-pitched voice and have a characteristic facial appearance. The large number of abnormal chromosomes in Bloom syndrome causes a higher risk for different types of childhood cancer, including leukemia, osteosarcoma and Wilms tumour.
Fanconi anemia affects the bone marrow so it doesn’t make enough healthy red blood cells, white blood cells or platelets. Children with Fanconi anemia have a higher risk for leukemia.
Ataxia-telangiectasia (AT) affects the nervous system, immune system and other body systems. Children with AT often have a weakened immune system and a higher risk of developing cancer, particularly lymphoma and leukemia.
Neurofibromatosis type 1 (also called von Recklinghausen disease) affects the development and growth of nerve cells (called neurons) and causes tumours to grow on nerves. Children with neurofibromatosis type 1 have a higher risk of developing certain cancers, including brain cancer, leukemia, neuroblastoma and rhabdomyosarcoma.
Wiskott-Aldrich syndrome affects blood cells and cells of the immune system. Children with Wiskott-Aldrich syndrome have a low number of platelets, which can cause easy bruising and bleeding. They also have a higher risk of infection because some immune cells, such as T cells and B cells, don’t work properly. Children with Wiskott-Aldrich syndrome have a higher risk for some types of cancer, such as leukemia and lymphoma.
Klinefelter syndrome affects male sexual development and causes small testicles, enlarged breasts and lack of facial and body hair. It is linked with a higher risk for childhood leukemia.
Li-Fraumeni syndrome greatly increases the risk of developing several types of cancer, including breast cancer, osteosarcoma, soft tissue sarcoma, brain cancer and leukemia.
Shwachman-Diamond syndrome affects many parts of the body, including the bone marrow, pancreas and skeletal system. Children with Shwachman-Diamond syndrome often have lower levels of all types of blood cells. This causes more infections, fatigue, weakness and easy bruising or bleeding. Children with Shwachman-Diamond syndrome also have a higher risk for childhood leukemia.
Children who have a brother or sister with leukemia have a slightly higher risk of developing leukemia than children in the general population. In identical twins this risk is much higher. The risk is highest at birth and goes down until the child is 7 years of age.
Children exposed to high doses of radiation from nuclear reactor accidents have a higher risk of developing leukemia. Most leukemias that develop after exposure to radiation are AML but they can also be ALL.
Children who had radiation therapy to treat cancer or another health condition may have a higher risk of developing leukemia. Most leukemias that occur after radiation therapy are AML rather than ALL. The risk of developing AML is greater if both chemotherapy and radiation were used in treatment.
Children who had certain types of chemotherapy may have a higher risk for leukemia. Most leukemias that occur after previous chemotherapy are AML rather than ALL. The leukemia usually develops within 5 years after treatment.
A birth weight greater than 4000 g (8.9 pounds) has been linked to a higher risk for ALL.
The following factors have been linked with childhood leukemia, but there is not enough evidence to say they are known risk factors. More research is needed to clarify the role of these factors for childhood leukemia.
Exposure to low levels of radiation before birth and in early childhood is linked to ALL. This exposure can come from medical tests such as x-rays or CT scans. The risk of developing leukemia from exposure to low-level radiation is low.
Electromagnetic fields (EMFs)
A small number of studies suggest that EMFs from power lines could increase the risk for childhood leukemia.
Studies suggest that exposure to certain pesticides may be linked to a higher risk of developing childhood leukemia. This risk is associated with both a child’s direct exposure and a mother’s exposure during pregnancy. Pesticides are made from a large number of different chemicals, only some of which may be related to the risk for leukemia.
There is some association between childhood leukemia and the child’s parents smoking. There is also a link between this cancer and the mother being exposed to 2nd-hand smoke during pregnancy. The risk from cigarette smoke seems to be higher for childhood ALL.
Several studies suggest that a woman drinking alcohol during pregnancy is linked with a higher risk of childhood AML.
Benzene is a risk factor for leukemia in adults. Some research suggests that it may also be a risk factor for childhood leukemia. The child’s parents could be exposed to benzene in their workplace, or the child could be exposed to it through air pollution.
Mother’s exposure to paint
Some studies suggest that children of women who work as painters, either before or during pregnancy, may have a higher risk for childhood leukemia. It is not known which chemicals in paint may be responsible for this higher risk.
Unknown risk factors
It isn’t known whether or not the following factors are linked with childhood leukemia. It may be that researchers can’t show a definite link or that studies have had different results. More research is needed to see if the following are risk factors for childhood leukemia:
- exposure to radon
- less exposure to infections
Questions to ask your healthcare team
Ask your child’s healthcare team questions about risks.