Reviewed by Dr. Clement J. Cheng
Primary brain cancer is a relatively rare disease, accounting for only 1 percent of all cancers and 2.5 percent of all cancer deaths. Primary brain cancer is cancer that originates in the brain and should be distinguished from metastatic, or secondary, brain cancer. One in four patients with cancer originating elsewhere in the body will develop metastatic brain cancer; only 10 to 12 people of 100,000 are diagnosed with primary brain cancer every year.
Brain tumors rarely metastasize outside the brain, unlike other cancers whose cells multiply uncontrollably. Brain tumors can be either benign or malignant (cancerous), but no brain tumor is harmless. Any mass in the skull can put undue pressure on sensitive brain tissue, threatening neurological function and life. Many brain tumors are asymptomatic until they reach a certain size.
Brain cancer may be genetic, but its exact cause is unknown. Chemicals such as vinyl chloride and some pesticides may be responsible for it in some cases.
Several types of primary brain tumors exist:
- Meningiomas: These are the most common brain tumors, accounting for approximately 24 percent of cases. Most tumors of this type are benign (85 percent) and curable with surgery. However, some of these tumors are located close to vital parts of the brain and cannot be cured with surgery alone.
- Glioblastoma: This is the most common malignant primary brain tumor. It grows rapidly and accounts for 23 percent of primary brain tumors. Patients usually must undergo a combination of surgery, chemotherapy, and radiation to treat glioblastoma. Less than 9 percent of glioblastoma patients survive two years, 3.4 percent survive five years, and 2.3 percent survive 10 years. Long-term survival is impossible.
- Astrocytoma and pituitary tumors: These tumors account for 8 percent of primary brain tumors. These tumors come in four grades, spanning from one to 4 on a scale of least to most malignant. Most astrocytomas cannot be cured. Pilocytic astrocytomas and subependymal giant cell astrocytomas are two types that have good prognosis. Patients with these brain tumors usually undergo a combination of surgery, chemotherapy, and radiation therapy. About 43 to 63 percent of these patients live two years, 30 to 48 percent live five years, and 21 to 36 percent survive 10 years. Generally, the less malignant the cancer, the better the survival rate.
- Schwannomas: Schwannomas, also called nerve sheath tumors or acoustic neurons, are usually benign. They form in the part of the cranial nerve responsible for balance and hearing. They account for approximately 6 percent of primary brain tumors.
- Anaplastic astrocytoma: Anaplastic astrocytomas account for approximately 4 percent of primary brain tumors. Patients with these tumors usually undergo surgery, chemotherapy, and radiation therapy to treat them. Two-year survival is at 45 percent. Five-year survival is at 30 percent. Ten-year survival is at 21 percent.
- Oligodendrogliomas: Three percent of brain tumors are of this type. Generally, they cannot be removed with surgery alone. Seventy-seven percent of people diagnosed with this type of cancer live two years, 61 percent live five years, and 44 percent live 10 years.
