Brain Cancer

Brain cancer is a malignant tumor that originates in the brain.

Billy was a 16-year-old high school junior when he first began experiencing headaches and blurry vision. Over a period of several months his symptoms worsened. Billy lost interest in sports and most everything else. All he wanted to do was sleep. Billy's parents took him to the local hospital where he was rushed in for an emergency magnetic resonance imaging (MRI * ). It showed a tumor * growing in Billy's brain, causing a buildup of fluid that created pressure in his skull. That explained why Billy was having terrible headaches.

Billy was admitted to the hospital's pediatric cancer ward. Surgeons inserted a temporary shunt * to drain the excess fluid from his brain. Two weeks later, a team of neurosurgeons removed the tumor. For the next year and a half, Billy underwent radiation therapy * to kill the cancer cells that remained after surgery. Two years later, Billy was back in school, doing well and playing sports again.

Brain cancers are primary malignant * tumors that originate in brain cells. Often the term brain tumor is used instead of brain cancer because all brain tumors—whether malignant or benign * —destroy normal brain tissue as they grow and most continue to grow unless they are completely removed or destroyed. Because the brain is enclosed within the skull, which allows no room to expand, any growth produces pressure that can destroy normal tissue. Most brain tumors in adults are secondary tumors rather than brain cancers, having spread to the brain from other parts of the body. In contrast, most brain tumors in children are primary tumors originating in the brain. Most primary brain tumors are located within the meninges * . Unlike most other cancers, brain cancer can spread through the brain but rarely metastasizes, which means spreads, to other parts of the body.

There are approximately 130 different forms of brain cancer. They are broadly categorized according to the type of brain cell in which they develop. No matter what the cell type, the two most important issues regarding any brain tumor are where it is located and how fast it is growing. Both of these issues can be addressed with the help of computed tomography * (CT) and MRI.

More than one-half of all brain tumors in children are gliomas that begin in glial cells * of the central nervous system * (CNS). There are three types of glial cells:

Sometimes, gliomas occur in the brain stem * or the optic nerve * , which connects the eye and brain, or are made up of mixed types of glial cells.

Most gliomas, including those in children, are astrocytomas that begin in astrocytes. It is estimated that astrocytomas make up 75 percent of all gliomas. Whereas adult astrocytomas occur most often in the cerebrum * , childhood astrocytomas also arise in the cerebellum * or brain stem and metastasize throughout the brain, intermingling with normal brain tissue and making these tumors difficult to remove surgically.

Astrocytomas are classified according to how fast they grow:

The following low-grade childhood astrocytomas tend to have good prognoses:

Tumors originating in oligodendrocytes are called oligodendrogliomas. They usually occur in the cerebrum, grow slowly, and do not spread to surrounding tissue. They account for only about 4 percent of brain tumors and are most common in middle-aged adults.

Tumors arising in ependymal cells are called ependymomas. They account for almost 10 percent of brain tumors in children and can cause the ventricles to swell, leading to hydrocephalus * .

Many less-common brain tumors arise from cells other than glial cells:

Other types of brain tumors are much more common in children than in adults:

The chance that a person will develop a malignant tumor of the brain or spinal cord in his or her lifetime is less than 1 percent. Approximately 22,000 people are diagnosed with brain cancer each year. The survival rate depends upon the type of cancer cell.

Brain and central nervous system tumors are among the most common cancers in children from birth to 19 years old, and along with leukemia * , cause the most cancer-related deaths in children and teens less than 20 years old.

Symptoms of brain tumors depend on the size, type, and location of the tumor. Symptoms can be caused by a tumor pressing on a nerve or damaging an area of the brain. Symptoms might appear suddenly or gradually worsen over time. Tumors often cause edema—fluid buildup in brain tissue—leading to brain swelling and pressure. Headaches are one of the most common symptoms of a brain tumor, occurring in about 50 percent of patients.

In very young children, parents may notice an increase in head size and possibly bulging of the soft spots in the skull. Increased pressure in the brain can also cause:

Other common symptoms of brain tumors include:

About 50 percent of people with brain tumors have seizures at some point, and seizures are sometimes the first symptom of a brain tumor in children.

Diagnostic procedures for brain cancer include:

Although MRIs have generally replaced CT scans for diagnosing brain tumors, CT scans are sometimes used with children because CT scans are much faster and less confining. CT scans use radiation, however, and MRI relies on high-powered magnets to produce images.

A biopsy * is required to determine if a brain tumor is cancerous. If diagnostic imaging indicates that the tumor can be treated surgically, an operation called a craniotomy is performed to remove all or as much as possible of the tumor. A pathologist examines the tumor tissue during the operation in what is called a surgical or open biopsy. If the risk of surgery is too great—for example, if the tumor is near a vital area or deep within the brain—a stereotactic or needle biopsy is performed. With certain types of brain cancers, a spinal tap is performed to check for the spread of cancerous cells in the CSF.

The treatment and prognosis for brain cancer depend on the following factors:

Survival rates for brain cancer vary greatly. The prognosis is better for low-grade tumors and depends upon the type of cell affected.

Surgical removal of as much of the tumor as possible is the frontline treatment for brain cancer. Tumors that have spread widely cannot be cured surgically. However, surgery can reduce the amount of tumor that has to be treated with radiation or chemotherapy * and can prolong life. Surgery can also alleviate some symptoms of brain cancer or improve response treatment with medications such as antiseizure drugs.

Surgery alone or in combination with radiation therapy can cure many low-grade brain cancers, including noninfiltrating astrocytomas. When possible, surgery is also the primary treatment for infiltrating or diffusing astrocytomas. Most astrocytomas and oligodendrogliomas spread through the brain, mixing with normal cells, and are very difficult to remove surgically. Intermediate- or high-grade astrocytomas, including glioblastomas, cannot be cured by surgery alone. Ependymomas and meningiomas can sometimes be cured with surgery.

PNETs tend to grow fast and have a poorer prognosis. They are generally treated with surgery, followed by radiation and possibly chemotherapy. Medulloblastomas and gangliogliomas can often be cured with surgery alone or surgery plus radiation.

Other types of radiation therapy for brain cancer include:

Children younger than three years of age are not usually treated with radiation because of potential long-term effects on development. Chemotherapy may be used instead, and radiation treatment may be postponed until the child is older, or surgery may be repeated if the tumor returns.

Chemotherapy is used less often to treat brain cancer because most chemotherapy drugs do not cross the blood-brain barrier * . It is used to treat high-grade tumors in conjunction with surgery and/or radiation therapy. Sometimes chemotherapy drugs are placed directly on or near a tumor during surgery. For some brain tumors, chemotherapy is administered directly into the CSF in the brain or spinal canal. Lymphomas, medulloblastomas, and some oligodendrogliomas tend to respond better to chemotherapy than other brain cancers.

Even though brain cancer usually has no apparent cause, there are a few known risk factors * :

See also Brain Tumor • Cancer: Overview

* MRI, which is short for magnetic resonance imaging, produces computerized images of internal body tissues based on the magnetic properties of atoms within the body.

* tumor (TOO-mer) usually refers to abnormal growth of body tissue that have no known cause or physiologic purpose. Tumors may or may not be cancerous.

* shunt is a small tube inserted to move fluid from one area to another

* radiation therapy is a treatment that uses high-energy radiation from x-rays and other sources to kill cancer cells and shrink cancerous growths.

* malignant (ma-LIG-nant) refers to a condition that is severe and progressively worsening, such as cancer.

* benign (be-NINE) refers to a condition that is not cancerous or serious and will probably improve, go away, or not get worse.

* meninges (men-NIN-jeez) are the membranes that enclose and protect the brain and the spinal cord.

* computed tomography (komPYOO-tid toe-MAH-gruh-fee) or CT, is a technique in which a machine takes cross-sectional x-rays of the body to create a three-dimensional picture.

* glial cells are common support cells in the central nervous system that do not have electrical impulses.

* central nervous system (SEN-trul NER-vus SIS-tem) is the part of the nervous system that includes the brain and spinal cord.

* neurons are nerve cells. Most neurons have extensions called axons and dendrites through which they send and receive signals from other neurons.

* cerebrospinal fluid (seh-ree-bro- SPY-nuhl) is the fluid that surrounds the brain and spinal cord.

* cerebrum (suh-REE-brum) is the largest front and upper part of the brain that is responsible for mental processes.

* cerebellum (se-RUH-BEL-um) is the back portion of the brain that is responsible for muscle coordination and balance.

* brain stem is the part of the brain that connects to the spinal cord. The brain stem controls the basic functions of life, such as breathing and blood pressure.

* optic nerve is the nerve that sends messages, or conducts impulses, from the eyes to the brain, making it possible to see. The optic nerve is also referred to as the second cranial nerve.

* hydrocephalus (HY-droe-SEFuh- lus) is a condition, sometimes present at birth, in which there is an abnormal buildup of fluid within the skull, leading to enlargement of the skull and pressure on the brain.

* lymphoma (lim-FO-muh) refers to a cancerous tumor of lymphocytes, cells that normally help the body fight infection.

* lymphocytes (LIM-fo-sites) are white blood cells that play a part in the body's immune system, particularly the production of antibodies and other substances to fight infection.

* AIDS, or acquired immunodeficiency (ih-myoo-no-dih-FIH-shensee) syndrome, is an infection that severely weakens the immune system. It is caused by the human immunodeficiency virus (HIV).

* immune system (im-YOON SIStem) is the system of the body composed of specialized cells and the substances they produce that helps protect the body against disease-causing germs.

* leukemia (loo-KEE-me-uh) is a form of cancer characterized by the body's uncontrolled production of abnormal white blood cells.

* nausea (NAW-zha) refers to a feeling of being sick to one's stomach or needing to vomit.

* double vision is a vision problem in which a person sees two images of a single object.

* paralysis (pah-RAH-luh-sis) is the loss or impairment of the ability to move some part of the body.

* seizures (SEE-zhurs) are sudden bursts of disorganized electrical activity that interrupt the normal functioning of the brain, often leading to uncontrolled movements in the body and sometimes a temporary change in consciousness.

* convulsions (kon-VUL-shuns), also called seizures, are involuntary muscle contractions caused by electrical discharges within the brain and are usually accompanied by changes in consciousness.

* neurologic exam refers to systematic tests of how well various parts of the nervous system are functioning.

* positron emission tomography (POZ-i-tron e-MISH-en toe- MAH-gruh-fee), also called PET imaging or PET scanning, uses a special radioactive material called a tracer that is injected into the body. The material collects in the body's organs and tissues, allowing the radiologist to look for disease.

* biopsy (BI-op-see) is a test in which a small sample of skin or other body tissue is removed and examined for signs of disease.

* chemotherapy (KEE-mo-THER-apee) is the treatment of cancer with powerful drugs that kill cancer cells.

* blood-brain barrier is a biological shield in the body that helps prevent germs or other potentially harmful materials in the blood from entering the brain and spinal cord.

* risk factors are any factors that increase the chance of developing a disease.