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 non-Hodgkin lymphoma (NHL) develops in children who don’t have any of the risk factors described below.
The following are risk factors for childhood NHL. 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 to reduce a child’s risk of developing NHL if they have them.
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||Possible risk factors|
There is convincing evidence that the following factors increase the risk for childhood NHL.
Your immune system is a complex group of cells and organs that defend the body against infection, disease and foreign substances. Children with a weakened immune system have a higher risk of developing NHL. The immune system can be weakened for a number of reasons.
Immunosuppressant drugs affect the immune system so it doesn’t respond as it normally would. These drugs are used to prevent a child’s immune system from attacking a new organ after a transplant. But immunosuppressant drugs also lower the body’s natural ability to defend itself. Children who have had an organ transplant and are taking immunosuppressant drugs have a higher risk of developing NHL.
HIV (human immunodeficiency virus) and AIDS (acquired immunodeficiency syndrome) weaken the immune system. Children with HIV or AIDS have a greater risk of developing childhood NHL.
An immunodeficiency disorder affects the immune system’s natural ability to defend the body against micro-organisms that cause infection. A hereditary immunodeficiency disorder is inherited, so it is present at birth. It is caused by a genetic mutation. The following are rare hereditary immunodeficiency disorders that increase a child’s risk of developing NHL.
Ataxia-telangiectasia (AT) 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 have a higher risk of developing some cancers, including lymphoma and leukemia.
Wiskott-Aldrich syndrome affects blood cells and cells of the immune system. Children with Wiskott-Aldrich syndrome have lower numbers of platelets, which can cause easy bruising and bleeding. They also have a higher risk for infection because their immune cells (such as T cells and B cells) don’t work properly. Children with Wiskott-Aldrich syndrome also have a higher risk of developing some types of cancer, such as leukemia and lymphoma.
X-linked lymphoproliferative syndrome affects the immune system so it doesn’t respond the way it normally would to infection with the Epstein-Barr virus. Children with X-linked lymphoproliferative syndrome have a higher risk of developing NHL.
Chediak-Higashi syndrome affects the immune and nervous systems. Children with Chediak-Higashi syndrome have a higher risk of developing certain cancers of the immune system, such as lymphoma.
Severe combined immunodeficiency disorder (SCID) severely weakens the immune system. When children have SCID, their T cells and B cells don’t work normally. They have a high risk of developing serious infections and certain types of cancer, such as lymphoma.
Epstein-Barr virus (EBV) is a type of herpes virus that causes infectious mononucleosis (also called mono, or the kissing disease).
Children with EBV infection have a higher risk of developing Burkitt lymphoma, a type of B-cell lymphoma. This type of childhood NHL is most often found in Africa, where children may also be infected with malaria. In Canada, EBV is usually linked to NHL in children with weakened immune systems.
Children who were given chemotherapy or chemotherapy and radiation therapy to treat Hodgkin lymphoma have a slightly higher risk of developing NHL. The risk is higher when both chemotherapy and radiation therapy were used. Experts don’t know if the higher risk is related to the treatment itself or if the original Hodgkin lymphoma develops into NHL.
The following factors have been linked with childhood NHL, but there is not enough evidence to show they are known risk factors. Further study is needed to clarify the role of these factors for childhood NHL.
Some studies have suggested there may be a link between exposure to pesticides and the risk of developing childhood NHL.
Some studies have suggested there may be a link between a woman smoking during pregnancy and the risk of the child developing childhood NHL.
Ask your child’s healthcare team questions about risks.