No one knows what causes brain tumors; there are only a few known risk factors that have been established by research. Children who receive radiation to the head have a higher risk of developing a brain tumor as adults, as do people who have certain rare genetic conditions such as neurofibromatosis or Li-Fraumeni syndrome. But those cases represent a fraction of the approximately 35,000 new primary brain tumors diagnosed each year. Age is also a risk factor -- people over the age of 65 are diagnosed...
Brain tumors account for 85% to 90% of all primary central nervous system (CNS) tumors. Available registry data from the Surveillance, Epidemiology, and End Results (SEER) database for 2007 indicate that the combined incidence of primary invasive CNS tumors in the United States is 6.36 per 100,000 persons per year with an estimated mortality of 4.22 per 100,000 persons per year. Worldwide, approximately 238,000 new cases of brain and other CNS tumors were diagnosed in the year 2008, with an estimated 175,000 deaths. In general, the incidence of primary brain tumors is higher in whites than in blacks, and mortality is higher in males than in females.
Few definitive observations on environmental or occupational causes of primary CNS tumors have been made. Exposure to vinyl chloride may predispose to the development of glioma. Epstein-Barr virus infection has been implicated in the etiology of primary CNS lymphoma. Transplant recipients and patients with the acquired immunodeficiency syndrome have substantially increased risks for primary CNS lymphoma.[2,5] (Refer to the PDQ summary on Primary CNS Lymphoma Treatment for more information.)
The glial cell tumors, anaplastic astrocytoma and glioblastoma, account for approximately 38% of primary brain tumors. Since anaplastic astrocytomas represent less than 10% of all CNS gliomas, phase III randomized trials restricted to the anaplastic astrocytomas are not practical. Meningiomas and other mesenchymal tumors account for approximately 27% of primary brain tumors.
Other less-common primary brain tumors include the following in decreasing order of frequency:
Schwannomas, meningiomas, and ependymomas account for up to 79% of primary spinal tumors. Other less common primary spinal tumors include sarcomas, astrocytomas, vascular tumors, and chordomas, in decreasing order of frequency. The familial tumor syndromes (and respective chromosomal abnormalities that are associated with CNS neoplasms) include neurofibromatosis type I (17q11), neurofibromatosis type II (22q12), von Hippel-Lindau disease (3p25-26), tuberous sclerosis (9q34, 16p13), Li-Fraumeni syndrome (17p13), Turcot syndrome type 1 (3p21, 7p22), Turcot syndrome type 2 (5q21), and nevoid basal cell carcinoma syndrome (9q22.3).[6,7]