Brain tumors rarely metastasize to other organs. However, if a cancerous tumor spreads to other parts of the brain or spinal cord, the patient's prognosis is poorer than when the tumor is localized, explains the National Cancer Institute. Other important prognostic factors include the location, type and grade of the tumor; the patient's age; and how much of the tumor remains after surgery. The person's functional status, or ability to perform everyday activities, is an important factor as well.
Doctors classify brain cancers according to the type of cells involved and the tumor's grade, which is a function of how closely the tumor cells resemble normal cells when viewed under a microscope, advises the National Cancer Institute. Grade I tumors differ little from healthy tissue, while grade IV tumors differ from healthy tissue a great deal. Low-grade tumors typically correlate with a better prognosis.
For example, astrocytoma is a common type of brain cancer that occurs in children and adults, according to the National Brain Tumor Society. Grade I astrocytoma, or pilocytic astrocytoma, is a slow-growing tumor that typically occurs in children and teens. By contrast, grade IV astrocytoma, or glioblastoma multiforme, is an extremely aggressive tumor that occurs mostly in adults. It spreads widely and quickly to many parts of the brain, making complete surgical removal impossible. The median survival rate for patients with this type of tumor is about 15 months. Only 4 percent of patients survive for five years.