A risk factor is anything that might increase a person's chance of getting cancer. Risk factors can be lifestyle-related, genetic (inherited), or environmental.

Lifestyle-related risk factors: These include the effect of sunlight exposure, diet, amount of exercise, and harmful habits such as smoking and drinking alcohol. In general, lifestyle-related factors are the most significant influence contributing to cancers in adults, but they are not part of childhood cancer risk.

Immune system disorders: Certain genetic diseases cause children to be born with an abnormal or deficient immune system. In addition to developing serious infections because of reduced immune defenses, these children also have an increased risk of developing non-Hodgkin lymphoma.

Although these congenital (present at birth) immune deficiency diseases can be passed on to children, non-Hodgkin lymphoma survivors who do not have these inherited diseases do not pass on an increased risk of non-Hodgkin lymphoma to their children.

Patients with transplanted organs (kidney, heart, liver) are treated with drugs that weaken their immune system to prevent it from attacking the new organs. This intentional immune suppression carries a significant risk of the patient developing non-Hodgkin lymphoma that is almost always caused by Epstein-Barr virus infection. The exact risk depends on which drugs are used to prevent transplant rejection.

Infection with human immunodeficiency virus (HIV), also known as the AIDS virus, is an increasingly common cause of immune system deficiency in children and adults. As with congenital and drug-related immune deficiencies, HIV infection is a risk factor for developing non-Hodgkin lymphoma. Children with non-Hodgkin lymphoma may be tested for HIV infection.

Environmental risk factors: Radiation and chemicals are influences in our surroundings. Radiation injury generally is only a very minor risk factor in childhood non-Hodgkin lymphoma. Survivors of atomic bombs and nuclear reactor accidents have an increased risk of developing several types of cancer. Although leukemia and thyroid cancers are the most common, there is a slightly increased risk of non-Hodgkin lymphoma as well.

Previous cancer treatment: Patients treated with radiation therapy for other cancers have a slightly increased risk of developing non-Hodgkin lymphoma later in life. However, it usually takes many years for this to happen, so these secondary cases of non-Hodgkin lymphoma are more common in adults than children. Patients treated with both chemotherapy and radiation therapy are more likely to develop leukemia or non-Hodgkin lymphoma as a result of this treatment.

Other infections: In areas of Africa where Burkitt lymphoma is common, chronic infection with both malaria and the Epstein-Barr virus (EBV) is an important risk factor. The form of Burkitt lymphoma commonly seen in non-African children is sporadic, with no obvious geographic distribution.

It is important to remember that most children and adults with non-Hodgkin lymphoma have no known risk factors. There is nothing these children or their parents could have done to prevent this cancer.

Revised: 03/08/2007