Risk Factors for Brain and Spinal Cord Tumors

A risk factor is anything that increases your chances of getting a disease such as a brain or spinal cord tumor. Different types of cancer have different risk factors. Some risk factors, like smoking, you can change. Others, like your age or family history, can’t be changed.

But having a risk factor, or even several, does not always mean that a person will get the disease, and many people get brain or spinal cord tumors without having any known risk factors.

Many different types of tumors can start in the brain or spinal cord, and while they might have some things in common, these different tumors might not all have the same risk factors.

Most brain tumors are not linked with any known risk factors and have no obvious cause. But there are a few factors that can raise the risk of brain tumors.

Radiation exposure

The best known environmental risk factor for brain tumors is radiation exposure, most often from radiation therapy to treat some other condition. For example, before the risks of radiation were known, children with ringworm of the scalp (a fungal infection) were sometimes treated with low-dose radiation therapy, which was later found to increase their risk of some types of brain tumors as they got older.

Today, most radiation-induced brain tumors are caused by radiation to the head given to treat other cancers. They occur most often in people who received radiation to the brain as children as part of their treatment for leukemia. These brain tumors most often develop around 10 to 15 years after the radiation, but sometimes they might not appear until decades later.

Radiation-induced tumors are still fairly rare, but because of the increased risk (as well as the other side effects), radiation therapy is only given to the head after carefully weighing the possible benefits and risks. For most patients with other cancers in the brain or head, the benefits of radiation therapy far outweigh the risk of developing a brain tumor years later.

The possible risk from exposure to imaging tests that use radiation, such as x-rays or CT scans, is not known for sure. These tests use much lower levels of radiation than those used in radiation treatments, so if there is any increase in risk, it is likely to be very small. But to be safe, most doctors recommend that people (especially children and pregnant women) not get these tests unless they are clearly needed.

Family history

Most people with brain tumors do not have a family history of them, but in rare cases brain and spinal cord tumors do run in families. In general, patients with familial cancer syndromes tend to have many tumors that first occur when they are young. Some of these families have well-defined disorders, such as:

Neurofibromatosis type 1 (NF1)

This genetic disorder, also known as von Recklinghausen disease, is the most common syndrome linked to brain or spinal cord tumors. People with this condition have higher risks of schwannomas, meningiomas, and certain types of gliomas, as well as neurofibromas (benign tumors of peripheral nerves). Changes in the NF1 gene cause this disorder. These changes are inherited from a parent in about half of all cases. In the other half, the NF1 gene changes occur before birth in people whose parents did not have this condition.

Neurofibromatosis type 2 (NF2)

This condition, which is much less common than NF1, is associated with vestibular schwannomas (acoustic neuromas), which almost always occur on both sides of the head. It is also linked with an increased risk of meningiomas or spinal cord ependymomas. Changes in the NF2 gene are usually responsible for neurofibromatosis type 2. Like NF1, the gene changes are inherited in about half of cases. In the other half, they occur before birth in children without a family history.

Tuberous sclerosis

People with this condition may have subependymal giant cell astrocytomas (SEGAs), which are low-grade astrocytomas that develop beneath the ependymal cells of the ventricles. They may also have other benign tumors of the brain, skin, heart, kidneys, and other organs. This condition is caused by changes in either the TSC1 or the TSC2 gene. These gene changes can be inherited from a parent, but most often they develop in people without a family history.

Von Hippel-Lindau syndrome

People with this condition tend to develop benign or cancerous tumors in different parts of the body, including hemangioblastomas (benign blood vessel tumors) in the brain, spinal cord, or retina, as well as tumors of the inner ear, kidney, adrenal gland, and pancreas. It is caused by changes in the VHL gene. Most often the gene changes are inherited, but in some cases the changes happen before birth in people whose parents don’t have them.

Li-Fraumeni syndrome

People with this condition are at higher risk for developing gliomas, along with breast cancer, soft tissue sarcomas, leukemia, adrenal gland cancer, and certain other types of cancer. It is caused by changes in the TP53 gene.

Turcot syndrome

Turcot syndrome (also known as brain tumor-polyposis syndrome) describes people who have many colon polyps and an increased risk of colorectal cancer, as well as an increased risk for certain types of brain tumors. But this syndrome is actually made up of two different hereditary conditions:

• When linked with familial adenomatous polyposis (FAP), there is a mutation in the APC gene. In people with this gene mutation, brain tumors are typically medulloblastomas.
• When linked with Lynch syndrome (also known as hereditary non-polyposis colorectal cancer or HNPCC), the mutation is in one of the mismatch repair genes, such as MLH1 or PMS2. In people with one of these gene mutations, brain tumors are usually gliomas.

Other syndromes

Other inherited conditions are also linked with increased risks of certain types of brain and spinal cord tumors, including:

• Gorlin syndrome (basal cell nevus syndrome)
• Cowden syndrome

Some families may have genetic disorders that are not well recognized or that may even be unique to a particular family.

Having a weakened immune system

People with weakened immune systems have an increased risk of developing lymphomas of the brain or spinal cord (known as primary CNS lymphomas). Lymphomas are cancers of lymphocytes, a type of white blood cell that fights disease. Primary CNS lymphoma is less common than lymphoma that develops outside the brain.

A weakened immune system can be congenital (present at birth), or it can be caused by treatments for other cancers, treatment to prevent rejection of transplanted organs, or diseases such as acquired immunodeficiency syndrome (AIDS).

Factors with uncertain, controversial, or unproven effects on brain tumor risk

Cell phone use

Cell phones give off radiofrequency (RF) rays, a form of energy on the electromagnetic spectrum between FM radio waves and those used in microwave ovens, radar, and satellite stations. Cell phones do not give off ionizing radiation, the type that can cause cancer by damaging the DNA inside cells. Still, there have been concerns that the phones, whose antennae are built-in and therefore are placed close to the head when being used, might somehow raise the risk of brain tumors.

Some studies have suggested a possible increased risk of brain tumors or of vestibular schwannomas (acoustic neuromas) with cell phone use, but most of the larger studies done so far have not found an increased risk, either overall or among specific types of tumors. Still, there are very few studies of long-term use (10 years or more), and cell phones haven’t been around long enough to determine the possible risks of lifetime use. The same is true of any possible higher risks in children, who are increasingly using cell phones. Cell phone technology also continues to change, and it’s not clear how this might affect any risk.

These risks are being studied, but it will probably be many years before firm conclusions can be made. In the meantime, for people concerned about the possible risks, there are ways to lower your exposure, such as using the phone's speaker or an earpiece to move the phone itself away from the head.

For more on this topic, see Cellular Phones. 

Other factors

Other environmental factors such as exposure to vinyl chloride (a chemical used to manufacture plastics), petroleum products, and certain other chemicals have been linked with an increased risk of brain tumors in some studies but not in others.

Exposure to aspartame (a sugar substitute), exposure to electromagnetic fields from power lines and transformers, and infection with certain viruses have been suggested as possible risk factors, but most researchers agree that there is no convincing evidence to link these factors to brain tumors. Research on these and other possible risk factors continues.