A central nervous system carcinoma is a malignant tumor arising in the cells of the brain or spinal cord.
Description
The central nervous system (CNS) is comprised of the brain and spinal cord. The CNS takes its name from the crucial role it plays in maintaining physical and mental well-being (homeostasis). The brain controls and monitors the body's activity; the spinal cord conveys information to the body from the brain, and vice versa. Consequently, a tumor in the CNS disrupts motor (e.g., standing, walking, writing) and sensory (e.g., seeing, tasting, hearing) activities.
The two major components of brain tissue are neurons (nerve cells) and glial cells. About half of all malignant CNS tumor growth starts in glial cells. Long thought to be mere space-holders, glial cells have been found to be extremely important. These cells actually protect and nourish the neurons, and may also help them transmit information. There are many different types of glial carcinomas, or gliomas.
The three layers of tissue, meninges, that cover the brain and spinal cord; and the pituitary and pineal parts of the brain, are also common sites for tumor growth. About 40% of benign (noncancerous) CNS tumors occur in the meninges, and the pituitary and pineal glands.
Some cancers that originate in organs, such as the kidneys, spread (metastasize) to the brain and spinal cord. These metastases differ from CNS carcinomas, however.
Demographics
About 35, 000 cases of CNS carcinoma are diagnosed each year. The Central Brain Tumor Registry of the United States (CBTRUS) puts the incidence of CNS tumors at 12.8 per 100, 000 person-years. The rate is slightly higher in males and slightly lower in females. Over a lifetime the chance a man will be diagnosed with and die from a CNS tumor is 1 in 200 and for a woman that rate is 1 in 263.
The older a person is the more likely he or she is to be diagnosed with CNS carcinoma. According to CBTRUS, the pediatric (individuals ages 0-19 years) incidence of CNS tumors is significantly lower, or about 3.8 per 100, 000 person-years. People under the age of 20 years also have a higher survival rate. They are five times more likely to live at least five years with a CNS tumor than are people between the ages of 45 and 64 years.
In addition to the diagnoses of primary CNS tumors (those that originate in the brain and spinal cord) is the diagnoses of metastatic cancer. Metastatic cancers are those that have spread from other primary sites, such as the breast, prostate, lungs, and colon. For every person diagnosed with a primary CNS tumor, at least four other individuals will be diagnosed with cancer that has metasta-sized to the brain and spinal cord. Occasionally, the identification of a metastatic brain cancerleads a physician to discover a cancer in another organ, or the primary site.
Causes and symptoms
The cause of CNS carcinoma is unknown. Important factors might include heredity, genetic make-up, and exposure to radiation and chemicals. Head injury might lead to meningiomas (carcinoma of the meninges). Extra or missing chromosomes or other genetic abnormalities are linked to the development of some CNS tumors. In one study a group of researchers led by T. Ballard showed pilots and flight attendants are at greater risk for CNS carcinoma, perhaps because of their frequent exposure to high levels of cosmic radiation.
Many individuals display no symptoms of CNS carcinoma until the tumor has grown large enough to exert pressure on part of the CNS. Because the skull covers the brain and the vertebral column protects the spinal cord, a growing tumor soon pushes up against a barrier of bone. The bone limits the expansion of the tumor and the cancerous and adjacent parts of the CNS become distorted. The meninges then swell in response to the distortion, producing symptoms.
When a tumor is in the spinal cord, symptoms include back pain and incontinence (inability to control defecation and urination). Paralysis on one side of the body (hemiparesis), which often indicates a stroke in an elderly person, sometimes occurs because of a brain tumor.
Diagnosis
Seizures and difficulties with walking, speech, sight, or other day-to-day activities usually cause patients with CNS carcinoma to consult a physician. The techniques a physician uses to diagnose CNS carcinoma begins with an examination and medical history. Some combination
of blood tests, x ray, computed tomography (CT), and magnetic resonance imaging (MRI) is used. If a tumor is detected with a CT or MRI scan a biopsy is usually done to determine the type of tumor.
Treatment team
A CNS carcinoma requires attention from several different types of physician specialists. A neurologist, a physician specializing in the nervous system, does the initial assessment. A radiologist interprets x rays, CT and MRI images. A hematologist or oncologist evaluates the results of blood tests. A pathologist studies the tissue from a biopsy. The surgery team that removes the tumor typically includes a neurosurgeon and an orthopedic surgeon. The orthopedic surgeon takes part because it is necessary to cut through bone to reach the brain and maneuver around vertebrae to reach the spinal cord. At premier cancer centers teams of physicians work collaboratively with one person, usually an oncologist, taking the lead. Physical and occupational therapists who help with rehabilitation following treatment and surgery, and registered nurses who administer chemotherapy, are also part of the team.
Clinical staging, treatments, and prognosis
By studying tissue from the tumor and surrounding cells the oncologist determines whether the tumor is growing and, if so, how fast. There is an elaborate system for assigning grades to the tumors that depends on things such as which part of the brain was served by the glial cell(s) in which the tumor began.
A plan for treatment is based on the location, size, and rate of growth of the tumor. Surgical removal of the tumor, radiation, and chemotherapy are all used. Method of treatment depends on the type of CNS carcinoma. In some cases the treatment is strictly palliative (provides comfort) and is not expected to halt the course of the cancer. Drugs, such as steroids, are often given to reduce swelling and, correspondingly, reduce pain and other symptoms.
About three-quarters of all individuals diagnosed with CNS carcinoma die before attaining a five-year survival rate.
Being an active participant in the treatment team, something that specialized cancer centers encourage, is one way to cope. Joining a support group also may help.
Clinical trials
The National Cancer Institute at the National Institutes of Health operates an information service that provides the most up-to-date information about clinical trials. The number is (800) 4-CANCER ([800] 422-6237).
Prevention
Limiting exposure to cosmic radiation and chemicals might lower the risk. However, experts have no specific recommendations for prevention.
Special concerns
Psychological changes as simple as mood swings and as severe as major changes in personality are possible. Sensory impairment is also possible. Advance directives, or written instructions for the care a person wants at each juncture of treatment, should be prepared and legalized as early in the therapeutic process as possible. Such directives make the patient's choices clear should he or she become unable to express them as the cancer progresses. Doing so relieves loved ones of the
responsibility for making those decisions, which can become extremely difficult.
Schold, S. Clifford Jr. et al. Primary Tumors of the Brain and Spinal Cord. Boston: Butterworth-Heinemann, 1997.
PERIODICALS
Ballard, T. et al. "Cancer Incidence and Mortality Among Flight Personnel: A Meta-Analysis" Aviation, Space, and Environmental Medicine. 71 (March 2000): 216-24.
Black, P. M. "Brain Tumors" (part two) New England Journal of Medicine 324 (May 31, 1991): 1555-1564.
Huncharek, M. et al. "Chemotherapy Response Rates in Recurrent/Progressive Pediatric Glioma; Results of a Systematic Review" Anticancer Research 19 (July-Aug. 1999): 3569-74.
ORGANIZATIONS
American Brain Tumor Association. 2720 River Road, DesPlaines, IL 60018 (800) 886-2282 <http://www.abta.org>
The Brain Tumor Society. 124 Watertown Street, Suite 3-H, Watertown, MA 02472. (617) 924-9997 <http://www.tbts.org>
—Tissue sample taken from body for microscopic examination.
Carcinoma
—A cancer that originates in cells that developed from epithelial tissue, a tissue that forms layers and often specializes to cover and protect organs.
Computed tomography (CT)
—X rays aimed at sections of the body (by rotating equipment) and images appear as slices. Results are assembled with a computer to give a three-dimensional image.
Homeostasis
—Self-regulating mechanisms are working, body is in equilibrium, no uncontrolled cell growth.
Magnetic resonance imaging (MRI)
—Magnetic fields and radio frequency waves are used to make images of the inside of the body.
Meninges
—The three layers of tissue that cover the brain and spinal cord.
Pineal
—A very small gland in the center of the brain that is sensitive to light.
Pituitary
—A gland at the base of the brain that produces hormones.
