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Cancers of the Mouth & Throat
A Patient's Guide to Treatment
By William M. Lydiatt, Perry J. Johnson, Jack Kusler
Addicus Books, Inc.Copyright © 2012 William Lydiatt, M.D., and Perry Johnson, M.D.
All rights reserved.
Cancers of the Mouth and Throat
If you have cancer, you are not alone. Each year, nearly 50,000 Americans develop a cancer of the lip, mouth, tongue, tonsils, throat, larynx, salivary glands, nose, and sinuses. Nearly 75 percent of these new cases are men. The incidence of mouth and throat cancer among women is, however, on the rise. As many as 500,000 are survivors of these cancers.
What Is Cancer?
Cancer is a group of cells growing out of control. Let's take a closer look at how this process occurs. Our cells contain a complicated set of instructions called DNA. These instructions tell a cell how to perform its job — that is, how to be a skin cell, a brain cell, a liver cell, and so on. They also tell the cell when to reproduce and when to die. DNA is the major constituent of our chromosomes, which determine what species we are and also what our individual traits will be, from our height and hair color to many aspects of our personality. Thus, DNA is often called the "building block" of life.
Sometimes, though, DNA can tear down what it has built. If a cell's DNA is damaged — for example, by a virus or toxic substance — the cell will usually die. Occasionally, instead, the abnormal cell will begin reproducing rapidly, creating ever greater numbers of new cells that also carry the DNA damage.
The more abnormal a cell's DNA becomes, the more abnormally the cell will behave. In turn, this increasingly abnormal behavior creates more and more mistakes within the cell. These DNA "mistakes" are called mutations. It appears that damaged cells must have between six and ten different mistakes before they begin behaving like a cancer.
Take, for example, the cells that make up the mucous membrane of the mouth and throat. These cells normally divide and reproduce only when old cells die or other cells are scraped away in normal activities such as chewing and swallowing. Under strict DNA instructions, the cells next to those that have died or been scraped away will reproduce to replace them. Once the dead cells have been replaced, the process of cell replication stops.
However, if the cells are exposed to excessive tobacco smoke, alcohol, or other hazards, their DNA may be damaged. They may pass the damage on to the next generation of cells as they reproduce. As larger and larger generations of abnormal cells are formed, they may eventually become visible as white or red patches in the mouth or throat. These are known as precancerous lesions. With time, the lesions may increase in both size and abnormality until they finally become true cancers.
Unfortunately, the out-of-control cell growth that causes cancer does not usually stop with the formation of a single tumor. Instead, the abnormal cells tend to invade surrounding tissue and can spread even farther, through the blood or through the lymphatic system. The lymphatic system includes channels, similar to veins, that carry white blood cells and nutrients and drain waste products away from tissues and cells. These channels contain rounded masses of tissue called lymph nodes, which filter bacteria, viruses, and cancer cells out of the lymphatic fluid.
When cancer spreads beyond the place where the first abnormal cells develop, each resulting new cancer is called a metastasis. When a group of cells grows into a mass that does not invade or spread elsewhere, the mass is called a benign — that is, a noncancerous — tumor, and it has a much better prognosis than cancer.
Health professionals also speak of cancers in terms of "grade". The higher the grade, the more aggressive the cancer and the likelihood that the cancer will come back after treatment. Lymph node involvement is also more likely in high-grade than low-grade tumors. High-grade cancers are more likely to spread to other areas of the body.
Causes of Mouth and Throat Cancer
Smoking cigarettes, or chewing or sniffing tobacco can put a person at high risk for cancer. All forms of tobacco are dangerous, but cigarette smoke is probably the most dangerous. Most people automatically think of lung cancer when they think of the risks of smoking, but cancer can form at any site that has contact with tobacco or its by-products. In fact, 90 percent of people with mouth and throat cancer have been users of tobacco in some form.
The tissues of the mouth and throat are directly exposed to harmful chemicals in tobacco, including formaldehyde, benzo-a-pyrene, nitrogen oxides, urethane, nickel, cadmium, radioactive polonium, hydrazine, and nitrosodiethylamine. These are known to damage the DNA in the cells at the site of contact.
Tobacco products can also damage other areas of the body, including the sinuses, esophagus, salivary glands, lungs, even the kidneys and bladder. All these tend to be sensitive to the effects of tobacco. Damage to these more distant parts of the body occurs after special proteins called enzymes have broken down the chemicals in tobacco. These enzymes reduce harmful substances to much smaller components that can be excreted through the urine. However, the broken-down products of tobacco can themselves be harmful. When the kidneys and bladder, for example, come into contact with these products, cellular damage can occur in those areas as well as in the mouth or throat.
Still, not everyone who uses tobacco will develop cancer, and some who have never used it will. In general, however, tobacco use is the biggest known cause of cancers of the mouth and throat. In fact, smoking 1 to 2 packs of cigarettes a day for 20 years or more gives you a risk of mouth or throat cancer that is 2 to 8 times greater than that of a nonsmoker. The more you smoke, the higher your risk. Women have a higher risk than men who smoke the same amount. One pack of cigarettes a day for a woman is roughly equivalent to 1.25 packs for a man.
Alcohol in large quantities (more than five drinks per day for men and somewhat fewer for women) is known to increase the risk of mouth and throat cancers — especially those at the floor of the mouth, base of the tongue, tonsils, and lower pharynx. As many as 80 percent of people with these cancers use alcohol regularly. Heavy drinking (five or more drinks per day) alone creates a risk that is five to eight times greater than that of a nondrinker. The combination of heavy alcohol use and tobacco use is particularly dangerous. For example, a person who consumes two packs of cigarettes and five drinks each day is about forty times more likely to get cancer than someone who does not smoke or drink. Hard liquor is probably riskier than beer, which is riskier than wine.
Overexposure to any of countless chemicals and hazardous substances can predispose people to a variety of cancers. Mouth and throat cancers have been linked, in particular, to mustard gas, wood dust, cadmium, leather manufacturing, isopropyl alcohol manufacturing, nickel, and chewing betel nut, a common practice in India.
Exposure to sunlight is also well known to increase the risk of skin cancers and lip cancer as well. Serious sunburns in childhood create risk for adult skin cancers. People with light skin and freckles, especially those of northern European descent, are at highest risk. It is important to use sun protection. Clothing that blocks the sun is best, since the use of sun-blocking creams is controversial. Some recent studies suggest the creams might actually raise the risk of sun damage, perhaps by giving users a false sense of security that prompts them to stay out in the sun longer. Other studies show a positive effect. Overall, the use of sun-blocking agents is probably better than no sunblock.
Severe stomach acid reflux can also elevate the risk of cancers of the esophagus and the lower throat. Exposure to radiation as a child creates a risk for cancer later, as an adult. A virus, human papilloma virus, has also been linked to some cancers of the throat.
Although some cancers appear to run in some families, cancers of the mouth and throat tend to be inherited only through rare genetic syndromes.
Li-Fraumeni syndrome is a mutation of a special gene that makes a protein necessary for repairing cellular damage. The mutation inhibits the repair process and therefore raises the risk of cancer.
Bloom's syndrome is associated with short stature, increased sun sensitivity, immune deficiency, and a higher risk of mouth cancer, especially of the lip and tongue.
Fanconi's anemia is associated with abnormal skin pigmentation, growth retardation, and blood abnormalities such as anemia, and this too carries an increased risk of mouth cancer.
Xeroderma pigmentosum involves extreme sensitivity to sunlight and puts affected individuals at a much higher risk for lip and skin cancers.
If you or any of your relatives have any of these syndromes, or if members of your family have had cancer, ask your doctor about your degree of risk. He or she might advise you to talk with a genetics counselor, who could help assess whether you or your family members may be at particular risk.
Areas of the Mouth and Throat Affected by Cancer
The mouth includes the lips, gums, teeth, tongue, hard palate (roof of the mouth), floor of the mouth, and inner cheeks. Each of these components plays a major role in the quality and sustenance of life. If any one of them is compromised by disease, it can threaten a person's ability to breathe, eat, or speak.
The throat aids in swallowing, allows the passage of breath, and produces sound. The tubelike pharynx handles swallowing. The muscles of the pharynx squeeze food down to the esophagus, a larger tubelike structure that takes over the job until the food reaches the stomach. The larynx, which is connected to the trachea (windpipe) and is actually part of the respiratory system, handles sound and breath.
The pharynx, or throat, is composed of the oropharynx, nasopharynx, and hypopharynx. "Oro" is Latin for mouth, and "pharynx" is derived from the Greek word for throat. Thus the oropharynx ("mouth-throat") begins at the back of the mouth and includes the tonsils, soft palate, uvula (that bit of tissue that hangs down at the back of your throat), and base (rearmost part) of the tongue. The nasopharynx ("nose-throat") is a very small area above the soft palate and behind the nose. It contains the adenoids, small masses of infection-fighting tissue that are part of the lymphatic system. The eustachian tube connects the middle ear to the nasopharynx. When fluids accumulate in the middle ear as a result of illness or infection, the eustachian tube may become swollen or blocked. The eustachian tube also produces the "pop" in your ears when you experience a change in altitude or air pressure. The hypopharynx ("under-throat") is difficult to see without special equipment. Located behind the larynx, it connects the pharynx to the esophagus.
The larynx, or voice box, is located in front of the pharynx and just below the back of the tongue. It can be felt in the neck as the Adam's apple. It has three compartments — the glottis, supraglottis, and subglottis.
The glottis is formed by the vocal cords, which tighten and loosen to produce sounds of varying pitch. The tongue, cheeks, teeth, and lips then shape the sounds into words. Pitch variation is an important, expressive aspect of speech but a minor requirement for basic communication.
The supraglottis, or top portion of the larynx, consists of a flap of cartilage called the epiglottis and other structures called false vocal cords, which we use for whispering. Together, these structures shunt food and liquids backward, away from the trachea and into the pharynx. This protects against choking and keeps food and liquids out of the lungs.
The subglottis is the space below the true vocal cords and just above the trachea.
The paranasal sinuses, located behind and beside the base of the nose, are air-filled cavities in the skull. They are lined with mucous membranes. Sinuses play an important role in speech — the sound made by your larynx and throat resonates in your sinuses, making your voice audible and giving it your characteristic sound. When you get a cold, your sinuses get congested and the membranes swell, giving the sound of your voice a nasal quality. The four major sinuses in your head are the frontal, maxillary, ethmoid, and sphenoid sinuses.
The frontal sinus, located above your eyes and behind your forehead, does not develop until adolescence. It determines the shape of your adult forehead, and the thick bones surrounding it protect your brain from injury. Tumors usually do not affect this sinus.
The sinuses most susceptible to tumors are the maxillary and ethmoid sinuses. The maxillary sinuses, located under your eyes, help form the floor of your eye sockets. They are the sinuses most frequently affected by sinus infections. Nerves that supply sensation to the middle part of your face and your top teeth run through this sinus. A tumor involving these nerves can create numbness or tingling of the face or upper teeth. Surgical removal of this sinus can also cause numbness in these areas. The ethmoid sinuses, containing nerves that create your sense of smell, are located between your eyes.
The bones that separate the sinuses are eggshell thin; however, they can play an important role in acting as a barrier to the spread of cancer. One such bone is the cribriform plate, located right on top of the ethmoid sinuses. This bone has many perforations through which the nerves for the sense of smell pass from the nose to the brain and back. Also, the dura, a thick covering of tissue, surrounds the brain and further inhibits the invasion of cancer cells. Still another barrier is the periorbita, the thick lining of the eye sockets which protects the eyeballs from the spread of a tumor.
The sphenoid sinus is situated almost in the center of your head. It is surrounded by the nasopharynx below, the brain on the top and three sides, and the nasal cavity in the front. It is the least common site for sinus tumors.
These glands produce saliva, which lubricates food for swallowing and contains special proteins called enzymes that begin the digestive process. There are three pairs of major salivary glands — the parotid, submandibular, and sublingual glands. The largest of these are the parotid ("around the ear") glands, located on each cheek, just in front of the ear and overlying part of the jawbone. The submandibular ("under jaw") glands are partially under each side of the lower jawbone. The sublingual ("under tongue") glands are inside the jawbone and under each side of the tongue.
There are also between 600 and 1,000 minor salivary glands within the mucous membranes that line your tongue, lips, palate, throat, nose, and sinuses. These glands cannot be seen without a microscope.
The neck contains nerves that permit most of the activities of the mouth and throat, including the nerves to the tongue, larynx, and pharynx. If cancer invades any of these nerves, it usually destroys or damages their function. For example, if the major nerve to the tongue is invaded, you will notice a slurring of speech, and if the nerve to the vocal cord is invaded, you will become hoarse.
The neck also contains the lymph nodes, the first areas to which mouth and throat cancers generally spread. The lymph nodes are small, bean-shaped glands that filter out bacteria, viruses, and cancer cells. They swell if they become infected or cancerous.
Types of Mouth and Throat Cancer
The type of a cancer is determined by its cell of origin. That is, where did the cancer start — in cells of the skin, fatty tissue, muscle, cartilage, or bone? Certain areas of the mouth and throat are more prone to cancers because they come into contact with cancer-causing substances. Determining the precise type of a cancer is important since treatment will be based on the type of cancer present.
Excerpted from Cancers of the Mouth & Throat by William M. Lydiatt, Perry J. Johnson, Jack Kusler. Copyright © 2012 William Lydiatt, M.D., and Perry Johnson, M.D.. Excerpted by permission of Addicus Books, Inc..
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