Risks for childhood leukemia

Some things can affect your risk, or chance, of developing cancer. Certain behaviours, substances or conditions can increase or decrease the risk. Most cancers are the result of many risks. Childhood cancers are rare and there is less known about the risks. Most childhood risks are not modifiable. This means that you can't change them. Until we learn more about the risks for childhood leukemia, there are no specific ways to lower the risk.

About 75% of all childhood leukemias are acute lymphoblastic leukemia (ALL). ALL develops more often in boys and usually occurs in children between the ages of 1 and 4 years. About 20% of all childhood leukemias are acute myeloid leukemia (AML). Childhood AML is more common in children before the age of 2 and in teenagers.

Some children with certain genetic conditions have a higher than average risk for childhood leukemia. Talk to your doctor about your child's risk.

The following can increase the 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 a chromosome disorder caused by an extra chromosome 21. It is linked with intellectual disability and a characteristic facial appearance. Children with Down syndrome have a higher risk of developing several medical conditions, including childhood leukemia.

Bloom syndrome is an inherited condition caused by mutations in a certain chromosome. Signs include shorter than average height, a high-pitched voice and a characteristic facial appearance. Bloom syndrome is associated with an increased risk of developing cancer, including leukemia, lymphoma, breast, cervical, colon, stomach, laryngeal and non-melanoma skin cancers, as well as Wilms tumour. People with Bloom syndrome often develop several different types of cancer.

Fanconi anemia is an inherited condition that affects the bone marrow so it cannot make red blood cells, white blood cells or platelets. Fanconi anemia increases the risk of AML, myelodysplastic syndromes, and oral and oropharyngeal cancers.

Ataxia-telangiectasia is an inherited disease that affects the nervous system, immune system and other body systems. Signs and symptoms include loss of balance, poor coordination, frequent infections, red eyes (due to widening of blood vessels) and abnormal eye movements. Ataxia-telangiectasia is associated with an increased risk of developing some cancers, including leukemia and lymphoma.

Neurofibromatosis type 1 is an inherited condition that affects the nervous system. It affects the development and growth of neurons (nerve cells), causes tumours (neurofibromas) to grow on nerves and may produce other abnormalities in muscles, bones and skin. Sometimes cancerous tumours called malignant peripheral nerve sheath tumours may grow along the nerves. Neurofibromatosis type 1 increases the risk of leukemia, neuroendocrine tumours, soft tissue sarcoma, brain tumours and neuroblastoma.

Wiskott-Aldrich syndrome is an inherited condition that affects the blood cells and the cells of the immune system. It usually only affects boys. Wiskott-Aldrich syndrome increases the risk of developing AML, Hodgkin lymphoma and non-Hodgkin lymphoma.

Li-Fraumeni syndrome is an inherited condition that is associated with an increased risk of developing certain types of cancers, including acute leukemia, breast cancer, brain tumours, soft tissue and bone sarcomas and adrenal cortical carcinomas. People with Li-Fraumeni syndrome tend to develop several different types of cancer before the age of 45.

Shwachman-Diamond syndrome is an inherited condition that affects the bone marrow, pancreas and bones. Shwachman-Diamond syndrome increases the risk of AML and myelodysplastic syndromes.

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, especially if leukemia develops in the first year of life.

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 have a higher risk of then developing leukemia. This risk is usually outweighed by the benefit of treating the original cancer.

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 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. This risk is usually outweighed by the benefit of treating the original cancer.

A birth weight greater than 4,000 g (8.9 pounds) increases the risk for ALL.

Exposure to the following have been linked with childhood leukemia, but more research is needed to know for sure that they are risks. The exposure studied could be exposure during childhood, in utero (before being born) or to sperm or egg before they join at conception.

• low levels of radiation in utero and in early childhood
• electromagnetic fields (EMFs) in childhood
• certain pesticides in utero or as a child
• either parent smoking tobacco (before conception) or in pregnancy
• second-hand smoke in childhood
• alcohol in utero
• benzene in utero, in childhood or through either parent's exposure before conception
• chemicals in paint (before conception or in utero)