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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.
Acute lymphoblastic leukemia (ALL) is the most common type of leukemia diagnosed in children. About 75% of all childhood leukemia cases are ALL. Most cases of childhood ALL occur in children between the ages of 1 and 4 years. More males than females develop ALL.
About 20% of all childhood leukemia cases are acute myelogenous leukemia (AML). More girls than boys develop 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.
There is convincing evidence that the following factors increase your risk for childhood leukemia.
Genetic syndromes are diseases or disorders caused by a mutation (change) in one or more genes. Having certain genetic syndromes can increase the risk of developing childhood leukemia.
Down syndrome is a genetic condition that is associated 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 an inherited condition caused by a large number of abnormal chromosomes. Children with Bloom syndrome are usually smaller than average, have a high-pitched voice and characteristic facial appearance. The large number of abnormal chromosomes in Bloom syndrome causes a higher risk for different types of childhood cancer, including leukemia, solid tumours and Wilms’ tumour.
Fanconi anemia is an inherited condition. It affects the bone marrow so that the person has a lower number of all types of blood cells. Children with Fanconi anemia have a higher risk of leukemia.
Ataxia-telangiectasia (AT) is an inherited condition that affects the nervous system, immune system and other body systems. Children with AT have problems with walking, balance, hand coordination and nerve function. They often have a weakened immune system and a higher risk of developing cancer, particularly lymphoma and leukemia.
Neurofibromatosis type 1 is an inherited condition that causes tumours to form from nerve tissue. These tumours may form in the skin, just under the skin and in cranial and spinal nerves. Children with neurofibromatosis type 1 have a higher risk of developing certain cancers, including brain cancer, leukemia, neuroblastoma and rhabdomyosarcoma.
Wiskott-Aldrich syndrome is an inherited condition that affects blood cells and cells of the immune system. Children with Wiskott-Aldrich syndrome have a lower 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 of some types of cancer, such as leukemia and lymphoma.
Klinefelter syndrome is a genetic condition that affects male sexual development. Klinefelter syndrome is associated with a higher risk of childhood leukemia.
Li-Fraumeni syndrome is an inherited condition that greatly increases the risk of developing several types of cancer, including breast cancer, osteosarcoma, soft tissue sarcoma, brain cancer and leukemia.
Shwachman-Diamond syndrome is an inherited condition that 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 sibling (brother or sister) with leukemia have a slightly higher risk (2–4 times greater) of developing leukemia. The risk is much higher among identical twins. If an identical twin develops childhood leukemia, the other twin has about a 20% chance of developing leukemia too. This risk is highest at birth, and decreases up until the age of 7.
Exposure to high doses of radiation is a risk factor for childhood leukemia. Survivors of the atomic bomb explosions in Japan during the Second World War have an increased risk of developing ALL. Children exposed to radiation from nuclear reactor accidents also have an increased risk of developing ALL. However, most leukemias that occur after exposure to radiation are AML rather than 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.
The following factors have been linked with childhood leukemia, but there is not enough evidence to say they are known risk factors. Further study is needed to clarify the role of these factors for childhood leukemia.
A birth weight greater than 4000 g (or 8.9 pounds) has been linked to a greater risk of childhood leukemia.
Exposure to low levels of radiation before birth has been linked to ALL. This exposure can come from some medical tests, such as x-rays or CT scans. The risk of developing leukemia from exposure to low-level radiation is low.
A small number of studies suggest that EMFs from power lines could increase the risk of 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 leukemia risk.
There is some association between parents smoking, or exposure to second-hand smoke, before a baby is born and childhood leukemia.
Several studies suggest that a woman drinking alcohol during pregnancy is associated with an increased risk of childhood AML.
Some studies have suggested that children of women who work as painters, either before or during pregnancy, may have a higher risk of childhood leukemia. It is not known which chemicals may be responsible for this increased risk.
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. Further study is needed to see if the following are risk factors for childhood leukemia:
Ask your child’s healthcare team questions about risks.