You Wanted to Know: Brain Cancer

doctor view output CT scan.

Even though brain cancer makes up only 2% of all cancers, rates of this deadly disease have been increasing over the past 50 years. Unfortunately, the average five-year survival rate for malignant brain tumors is only about 33%. This is one reason why it’s important to know your risk factors.

Elaine asked us about one of these risk factors on Twitter:


Brain tumors that start in the brain (primary tumors) are much less common than tumors that begin elsewhere in the body and spread to the brain (secondary tumors). Only about a third of primary brain tumors are malignant (cancerous), and the remainder are either benign or borderline malignant. These tumors may appear in the brain tissue itself or may grow in the membranes covering the brain (the meninges), in nerves, in the pituitary gland or the pineal gland.

Brain tumors occur when normal cells acquire changes in their DNA that make them grow and divide at an uncontrolled rate. Though the cause of primary brain cancer is not well understood, there are several things that may trigger this abnormal cell growth. Radiation therapy to the brain (as in treatment for brain or head cancers) is the most well-documented risk factor and increases risk for up to 20 or 30 years. Radiation from power lines, microwaves and cell phones has not been definitively linked to increased risk for brain tumors, but some studies have demonstrated a link between professions such as electrical work, farming or oil refinery work and increased brain tumors.

Only about 5% of brain cancers are due to genetic syndromes that raise risk for central nervous system tumors. These syndromes include neurofibromatosis types 1 and 2, von Hippel-Lindau syndrome, Li-Fraumeni syndrome, Turcot syndrome, basal cell nevus syndrome and familial glioma. Most of these uncommon syndromes also increase rates of many other types of tumors.

Taking care of your overall health and getting regular health screening is the best way to avoid brain cancer, especially since most brain cancers metastasize from elsewhere in the body. Cancers that commonly spread to the brain include breast, colon, kidney, lung and melanoma.