A risk factor is anything that increases a person's chance of getting a
disease such as cancer. Different cancers have different risk factors. For
example, exposing skin to strong sunlight is a risk factor for skin cancer.
Smoking is a risk factor for cancers of the lung, mouth, larynx, bladder,
kidney, and several other organs. But having a risk factor, or even several,
does not mean that a person will get the disease.
Lifestyle-related Risk Factors
Lifestyle-related risk factors for some cancers include an unhealthy diet,
harmful habits such as smoking and excessive drinking of alcohol, and excessive
sun exposure.
In general, lifestyle-related factors are the most significant influence
contributing to cancers in adults, but are the least important part of childhood
cancer risk.
There is some suggestion that drinking a lot of alcohol during pregnancy may
increase the risk of AML in the child.
Genetic Risk Factors
Certain genetic (inherited) diseases cause children to be born with an
abnormal or deficient immune system. In addition to developing serious
infections due to reduced immune defenses, these children also have an increased
risk of developing leukemia. (Although these immune deficiency diseases can be
passed on to children, adult leukemia survivors who do not have these inherited
diseases do not pass an increased risk of leukemia on to their children.)
There are also several other inherited disorders that increase a child’s risk
of developing leukemia:
- The Li-Fraumeni syndrome is a rare condition that increases a
person's risk of developing leukemia, bone or soft tissue sarcomas, breast
cancer, and brain tumors.
- Children with Down's syndrome (trisomy 21) have an increased risk
of developing leukemia. Instead of having two copies of each of the 23
chromosomes, children with Down's syndrome have three copies (one more than
usual) of chromosome 21. In ways that are not completely understood, this
extra chromosome 21 causes mental retardation and a characteristic facial
appearance. Children with Down's syndrome are 15 times more likely to
develop either ALL or AML than are other children. Down's syndrome is also
associated with transient leukemia - a leukemia-like condition within the
first month of life, which resolves on its own without the use of
chemotherapy.
- Klinefelter’s syndrome
is a genetic condition in which males have an
extra "x" chromosome. This causes infertility, prevents normal development
of male features (such as body hair, deep voice, etc.), and is also
associated with an increased risk of developing leukemia.
- Several other genetic disorders (neurofibromatosis, ataxia
telangectasia, Wiscott-Aldrich Syndrome, and Fanconi’s anemia) also carry an
increased risk of developing leukemia, but more commonly lead to
non-Hodgkin’s lymphoma and other types of cancers.
The sibling (brother or sister) of an identical twin who develops ALL or AML
before 6 years of age has a 20% to 25% chance of developing leukemia. Fraternal
(not identical) twins and other brothers and sisters have slightly increased
chances (2 to 4 times normal) of developing leukemia.
Environmental Risk Factors
Environmental risk factors are influences, such as radiation and certain
chemicals, in our surroundings that increase the likelihood of developing
diseases such as leukemias.
Radiation exposure: Radiation injury is a major environmental risk factor
in developing childhood leukemia. Japanese survivors of the atomic bomb had a
20-fold increased risk of developing AML, usually within 6-8 years after
exposure. Similar risks occurred after exposure to nuclear reactor accidents.
Exposure of the fetus to significant radiation within the first months of
development may also carry up to a 5-fold increased risk of developing ALL.
Radiation therapy and chemotherapy: Children and adults treated for other
cancers with radiation therapy and chemotherapy have a higher risk of developing
a second cancer, usually AML, later in life. Treatment with certain chemotherapy
drugs such as alkylating agents (a class that includes
cyclophosphamide and chlorambucil) and epipodophyllotoxins (such as etoposide
and teniposide) is associated with a higher risk
of second malignancy such as leukemia. These leukemias usually develop within 5
to 10 years of treatment and tend to be difficult to treat.
Immune system suppression: Patients who are receiving intensive therapy
to suppress their immune function (mainly organ transplant patients) are at
increased risk of developing cancer, especially of the lymphoid system. This
includes ALL.
Certain chemicals: Exposure to chemicals such as benzene may cause AML in
adults and, rarely, in children. ALL has not been linked to any cancer-causing
chemicals.
Other factors that have been studied for a possible association with ALL
include exposure to insecticides; mother’s age at birth; mother’s use of
alcohol, cigarettes, diethylstilbestrol (DES), or contraceptives; father’s
occupational exposure to chemicals and solvents; and chemical contamination of
ground water. None of these factors has been linked conclusively to ALL.
Revised 9-17-03
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