What causes someone to develop brain cancer?

Multi-factorial: The factors help contribute to all tumor development in general 1. Genetics 2. Mutation inducing factors (examples: smoking, drinking, etc). 3. Aging 3. Unknown causes (there are definitely people without family history or obvious "bad habits" that develop brain tumors).

Wish we knew: We know there are many factors which cause cancer. We know there are changes in genes in the dna of brain cells which can cause cancer. What we don't know is what causes that gene to change to start brain cancer. When we are able to identify the inciting event which causes a gene to change (mutate), we may be able to attack or prevent the cause instead of directing treatment at the cancer.