Brain cancer is a disease of the brain in which cancer cells (malignant) arise in the brain tissue. Cancer cells grow to form a mass of cancer tissue (tumor) that interferes with brain functions such as muscle control, sensation, memory, and other normal body functions. Tumors composed of cancer cells are called malignant tumors, and those composed of mainly noncancerous cells are called benign tumors.
Cancer cells that develop from brain tissue are called primary brain tumors while tumors that spread from other body sites to the brain are termed metastatic brain tumors. Statistics suggest that brain cancer occurs infrequently and is likely to develop in about 22,000 new people per year with about 13,000 deaths as estimated by the National Cancer Institute (NCI).
Not all brain tumors are alike, even if they arise from the same type of brain tissue. Tumors are assigned a grade depending on how the cells in the tumor appear microscopically.
The grade also provides insight as to the cell's growth rate. NCI lists the following grades:
Grade I: The tissue is benign. The cells look nearly like normal brain cells, and they grow slowly.
Grade II: The tissue is malignant. The cells look less like normal cells than do the cells in a grade I tumor.
Grade III: The malignant tissue has cells that look very different from normal cells. The abnormal cells are actively growing and have a distinctly abnormal appearance (anaplastic).
Grade IV: The malignant tissue has cells that look most abnormal and tend to grow quickly.
The most common primary brain tumors are usually named for the brain tissue type from which they originally developed. These are gliomas, meningiomas, pituitary adenomas, vestibular schwannomas, and primitive neuroectodermal tumors (medulloblastomas). Gliomas have several subtypes which include astrocytomas, oligodendrogliomas, ependymomas, and choroid plexus papillomas.
When the grades are coupled with the tumor name, it gives doctors a better understanding about the severity of the brain cancer. For example, a grade III (anaplastic) glioma is an aggressive tumor, while an acoustic neuroma is a grade I benign tumor. However, even benign tumors can cause serious problems if they grow big enough to cause increased intracranial pressure or obstruct vascular structures or cerebrospinal fluid flow.
Brain cancers are staged (stage describes the extent of the cancer) according to their cell type and grade because they seldom spread to other organs, while other cancers, such as breast or lung cancer, are staged according to so-called TMN staging which is based on the location and spread of cancer cells. In general, these cancer stages range from 0 to 4, with stage 4 indicating the cancer has spread to another organ (highest stage).
Although there are few early signs, the most common symptoms of brain cancer are weakness, difficulty walking, seizures, and headaches. Other common symptoms are nausea, vomiting, blurry vision, or a change in a person's alertness, mental capacity, memory, speech, or personality.
These symptoms can also occur in people who do not have brain cancer, and none of these symptoms alone or in combination can predict that a person has brain cancer.
Cancer can occur in any part of the brain (for example, occipital, frontal, parietal, or temporal lobes, brainstem, or meningeal membranes). A few brain cancers may produce few or no symptoms (for example, some meningeal and pituitary gland tumors).
The most frequently used test to detect brain cancer is a CT scan (computerized tomography). This test resembles a series of X-rays and is not painful, although sometimes a dye needs to be injected into a vein for better images of some internal brain structures.
Another test that is gaining popularity because of its high sensitivity for detecting anatomic changes in the brain is MRI (magnetic resonance imaging).
This test also resembles a series of X-rays and shows the brain structures in detail better than CT. MRI is not as widely available as CT scanning. If the tests show evidence (tumors or abnormalities in the brain tissue) of brain cancer, then other doctors such as neurosurgeons and neurologists that specialize in treating brain ailments will be consulted to help determine what should be done to treat the patient.
Occasionally, a tissue sample (biopsy) may be obtained by surgery or insertion of a needle to help determine the diagnosis. Other tests (white blood cell counts, electrolytes, or examination of cerebrospinal fluid to detect abnormal cells or increased intracranial pressure) may be ordered by the health-care practitioner to help determine the patient's state of health or to detect other health problems.
Primary brain tumors arise from many types of brain tissue (for example, glial cells, astrocytes, and other brain cell types). Metastatic brain cancer is caused by the spread of cancer cells from a body organ to the brain.
However, the causes for the change from normal cells to cancer cells in both metastatic and primary brain tumors are not fully understood. Data gathered by research scientists show that people with certain risk factors are more likely to develop brain cancer.
Individuals with risk factors, such as having a job in an oil refinery, handlers of jet fuel or chemicals like benzene, chemists, embalmers, or rubber-industry workers, show higher rates of brain cancer than the general population. Some families have several members with brain cancer, but heredity as a cause for brain tumors has not been proven.
Other risk factors such as smoking, radiation exposure, and viral infection (HIV) have been suggested but not proven to cause brain cancer. There is no good evidence that brain cancer is contagious, caused by head trauma, or caused by cell phone use.
Although many lay press and web articles claim that aspartame (artificial sweetener) causes brain cancer, the FDA maintains that it does not cause brain cancer and base their findings on over 100 toxicological and clinical studies regarding the sweetener's safety.
A treatment plan is individualized for each brain cancer patient. The treatment plan is constructed by the doctors who specialize in brain cancer, and treatments vary widely depending on the cancer type, brain location, tumor size, patient age, and patient's general health status. A major part of the plan is also determined by the patient's wishes. Patients should discuss treatment options with their health-care providers.
Surgery, radiation therapy, and chemotherapy are the major treatment categories for most brain cancers. Individual treatment plans often include a combination of these treatments. Surgical therapy attempts to remove all of the tumor cells by cutting the tumor away from normal brain tissue. This surgery is often termed invasive surgery to distinguish it from noninvasive radiosurgery or radiation therapy described below.
Radiation therapy attempts to destroy tumor cells by using high-energy radiation focused onto the tumor to destroy the tumor cells' ability to function and replicate. Radiosurgery is a nonsurgical procedure that delivers a single high dose of precisely targeted radiation using highly focused gamma-ray or X-ray beams that converge on the specific area or areas of the brain where the tumor or other abnormality is located, minimizing the amount of radiation to healthy brain tissue.
Equipment used to do radiosurgery varies in its radiation source; a gamma knife uses focused gamma rays, and a linear accelerator uses photons, while heavy-charged particle radiosurgery uses a proton beam.
Chemotherapy attempts to destroy tumor cells using chemicals (drugs) that are designed to destroy specific types of cancer cells. There are many chemical agents used; specific drug therapies are numerous, and each regimen is usually designed for the specific type of brain cancer and individualized for each patient.
For example, bevacizumab (Avastin) is a drug approved for treatment of glioblastomas. Chemotherapy can be administered intrathecally (by a surgically placed permanent reservoir in the brain), by lumbar puncture, by IV administration, and biodegradable chemically impregnated polymers. All treatments attempt to spare normal brain cells.
Other treatment options may include hyperthermia ( heat treatments ), immunotherapy (immune cells directed to kill certain cancer cell types), or steroids to reduce inflammation and brain swelling. These may be added on to other treatment plans.
Clinical trials (treatment plans designed by scientists and physicians to try new chemicals or treatment methods on patients) can be another way for patients to obtain treatment specifically for their cancer cell type. Clinical trials are part of the research efforts to produce better treatments for all disease types.
Stem cell treatments for brain and brain stem cancers and other conditions may be available, because research with patients is ongoing using these potential therapies. The best treatment for brain cancer is designed by the team of cancer specialists in conjunction with the wishes of the patient.