Brain tumors are a distinct category of cancer by virtue of their occurrence in a very separate and privileged region of the body called the central nervous system.
This system is protected by a barrier of bones and membranes and is bathed in a compartment of clear, sterile liquid called spinal fluid. For this and other unknown reasons, tumors that begin in the brain do not spread to the rest of the body. In contrast, brain metastases represent the spread of cancer to the brain from a primary location elsewhere in the body.
Brain tumors are also unique in that the cells that give rise to most brain tumors exist only in the brain. For example, glial cells surround and support the nerve-firing cells of the brain (called neurons) and give rise to gliomas, the most common category of brain tumor.
As in other cancers of other parts of the body, there are many types of brain tumors; the specific type, grade, and location of the tumor determine the treatment approach and prognosis. Surgery, radiation, and chemotherapy treatments are tailored to each case and are coordinated by a team consisting of a neurosurgeon, medical or neuro-oncologist, and radiation oncologist.
Glioblastoma multiforme is the most frequently occurring brain tumor in adults. It is usually detected after a person experiences unremitting headaches, seizures, or neurological impairment. Maximal surgical removal of the tumor is usually followed by radiation therapy to the “tumor bed” in combination with administration of an oral chemotherapydrug called temozolomide (Temodar). It appears that those brain tumors that do not produce a protein called MGMT respond better to Temodar than those that make the protein; MGMT protects cancer cell DNA from the damaging effects of Temodar. Tumor testing for MGMT has not been standardized and therefore is not routinely available.
One of the most exciting advances in our understanding of brain tumors was recently made when scientists discovered that brain tumor stem cells, comprising less than 1 percent of all the cells in any tumor, may be responsible for perpetuating the cancer. New therapies will undoubtedly hone in on this critical cell population and could lead to major advancements in the treatment of brain tumors.
