Brain Tumors: Primary

Description

Alternative Names

Risk Factors

An estimated 39,550 benign or malignant primary brain tumors are currently expected to be diagnosed in America this year. About 21,670 of these tumors will be malignant. Nearly 360,000 people in the US are currently living with brain cancer.Men are at higher risk for most brain tumors than women. Primary malignant brain tumors are still uncommon and represent only 1.3% of all cancers diagnosed in the United States and 2.4% of all deaths due to cancer.

Primary brain cancers are rare, occurring in slightly more than 11 people per 100,000 per year. There has been some evidence of a growing incidence of brain cancer among the elderly since the 1980s. The increase, however, is most likely due to the rise in incidence of non-Hodgkin's lymphomas--which can occur in the brain. When this malignancy is eliminated, any increase in other tumors is not significant.

Age

The average age of diagnosis for brain tumors is 57, and about 90% of primary brain tumors occur in adults, they can develop at all ages, usually peaking in two age groups:

• In adults between the ages of 55 and 65.
• In children between the ages of 3 and 12.

Risk Factors in Children. Tumors in the central nervous system are now the most common primary cancers in children, but they are still rare. An estimated 3,110 benign or malignant brain tumors are expected to be diagnosed in children each year. Brain tumors in children are more likely to occur in the cerebellum, the midbrain, or the optic nerve.

The incidence has increased over the past years, but there is some evidence that this increase is only due to better diagnostic procedures. The mortality rate has actually decreased. Researchers have attempted to uncover risk factors for childhood brain cancer. Some association between a higher risk and the following conditions have been observed:

• Children treated with radiation to the head for leukemia and who have a specific genetic defect may face a high risk for brain cancer. (It should be noted that for children without this defect, the risk is very small.)
• Having parents with specific cancers. (According to a 2000 study, having parents with nervous system cancers, colon cancer, or cancer in the salivary glands increased the risk of specific brain tumors in their children.)

Click the icon to see an illustrated series detailing colon cancer surgery.

Ethnicity

The risk for primary brain tumors in Caucasians is higher--as much as twofold depending on type--than in African Americans.

Environmental or Occupational Risk Factors

Radiation. The only proven risk factor for brain tumors to date is high-energy radiation from ions (such as with radiation treatment).

Studies on the effects of lower-energy radiation, such as microwaves and electromagnetic fields, have been uncertain. One study reported that men whose jobs exposed them to electromagnetic fields had higher rates for brain cancer, although a more recent study found a higher risk only in men who were also exposed to chemicals (petroleum, solvents, lead, pesticides and herbicides).

A 2002 study on Korean War veterans highly exposed to microwaves from radar equipment reported no excess risk for brain cancer--or any other malignancy--over a 40-year period. Studies in both 2000 and 2001 found no evidence to suggest a higher risk with cellular phones and other wireless devices that use radiofrequency.

Chemical and Metals in Brain Tumors. High exposure to a number of metals and chemicals have been associated with brain tumors, such as the following:

• High exposure to certain chemicals, including vinyl chloride and petroleum products, has been associated with brain tumors.
• High levels of lead, arsenic, or mercury exposure have been linked to a higher risk. One study suggested that lead exposure was particularly associated with meningiomas. It is unknown whether these associations are real, and confirmatory studies are needed.
• There has been some suggestion of a higher risk with exposure to pesticides.A major study of pesticides is underway, but results are not in yet. A 2003 study indicated that parental exposure to pesticides or herbicides did not appear to be important in increasing risk for brain cancer in their children.

Brain cancer is uncommon, and, over the course of their lifetime, many people are exposed to these chemicals, many of which are very common. To date, there has been no clear evidence that implicates any specific industrial chemical or metal.

Inherited Disorders

About 5% of primary brain tumors are associated with hereditary disorders. They include the following:

• Li-Fraumeni cancer family syndrome.
• Tuberous sclerosis.
• Von Recklinghausens disease (neurofibromatosis).
• Von Hippel Lindau disease.
• Familial polyposis (Turcot's syndrome).
• Osler-Weber-Rendu syndrome.

Organ Transplantation

A 2002 study reported a higher risk for brain cancers in patients who had undergone organ transplantations. Researchers believed that the drugs used to suppress the immune response after the procedures may increase the risk.

Medical Conditions Associated with a Lower Risk for Brain Tumors

A 2002 study reported lower risks for brain cancers in individuals with allergies and autoimmune diseases (e.g., diabetes type 1). Autoimmune diseases were also associated with a lower risk for meningiomas. The cause of this possible association remains unknown.

Studies have also found an association between lower risk for gliomas and a history of infection with varicella zoster, the virus that causes chicken pox and shingles.

Click the icon to see an image of the chicken pox.