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A risk factor is anything that affects 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. But risk factors don't tell us everything. Having a
risk factor, or even several, does not mean that a person will get the
disease, and many people who have no known risk factors get cancer.
Unlike many adult cancers, lifestyle-related risk factors do
not seem to play a large role in childhood cancers. On top of this,
very few risk factors for brain tumors have been found. There is no
clear cause for most brain tumors.
Environmental risk factors
The only well-established environmental risk factor for brain
tumors is radiation exposure to the head, which most often comes from
the treatment of other conditions. For example, before the risks of
radiation were well known (more than 50 years ago), children with
ringworm of the scalp (a fungal infection) often received low-dose
radiation therapy. This was found to increase their risk of brain
tumors later in life. Today, most radiation-caused brain tumors are the
result of radiation to the head given to treat other cancers such as
certain leukemias.
Inherited and genetic conditions
In rare cases (less than 1 in 10 brain tumors), children may
have inherited abnormal copies of genes from a parent that put them at
increased risk for certain types of brain tumors. In some cases, the
abnormal genes are not inherited but occur as a result of changes
(mutations) in the gene before birth.
People with inherited tumor syndromes often have many tumors
that start when they are young. Some of the more well-known disorders
are listed below.
Neurofibromatosis
type 1 (von Recklinghausen disease): This is the most
common inherited cause of brain or spinal cord tumors. Children with
this syndrome may have optic gliomas or other gliomas of the brain or
spinal cord, or neurofibromas (benign tumors of peripheral nerves).
Changes in the NF1 gene cause this disorder.
Neurofibromatosis
type 2: Less common than von Recklinghausen disease, this
condition is associated with cranial or spinal nerve schwannomas,
especially acoustic neuromas. It is also linked to an increased risk of
meningiomas, as well as spinal cord gliomas or ependymomas. Changes in
the NF2 gene are responsible for neurofibromatosis type 2.
Tuberous
sclerosis: This condition may be associated with
subependymal giant cell astrocytomas, as well as with other benign
tumors of the brain, skin, heart, or kidneys. It is caused by changes
in either the TSC1 or the TSC2 gene.
Von
Hippel-Lindau disease: Children with this disease have an
inherited tendency to develop hemangioblastomas (blood vessel tumors)
of the cerebellum, spinal cord, or retina, as well as kidney cancer. It
is caused by changes in the VHL gene.
Li-Fraumeni
syndrome: People with this syndrome have an increased risk
of gliomas, as well as breast cancer, soft tissue sarcomas, leukemia,
and adrenal gland cancers. It is caused by changes in the p53 gene.
Other inherited conditions, including Gorlin syndrome, Turcot
syndrome, Cowden syndrome, and hereditary retinoblastoma are also
linked with increased risks of certain types of brain and spinal cord
tumors. Some families may have genetic disorders that are not well
recognized or that may even be unique to a particular family.
Last Medical Review: 04/07/2008
Last Revised: 05/13/2009
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