no one knows what causes brain tumors; there are only a few known risk factors that have been established by research. people who receive radiation therapy to the head as a child have a higher risk of a brain tumor over the next 20 to 30 years. people who have certain rare genetic conditions such as neurofibromatosis -- a disorder of the nervous system -- or li-fraumeni syndrome -- a condition that predisposes someone to developing cancer -- are also at higher risk. but radiation therapy or rare genetic disorders are only a factor in a small number of the approximately 35 000 new primary brain tumors diagnosed each year. finally age is a factor. the rate of developing brain cancer is four times the rate each year in people over the age of 65 than in people younger than 65.
what causes brain tumors?