Monday, March 21, 2011

Tobacco Smoking and Alcohol Consumption are the Main Risk Factors for Larynx Cancer

What is the Larynx?

The larynx, or voice box, is an area in the throat that contains an intricate mixture of cartilage and muscles. Not only is it responsible for producing our voice, but also performs other complex functions such as protecting our airway during swallowing. The larynx is divided into three separate regions: the supraglottic larynx, the glottis, and the subglottic larynx. The glottis is the region that contains the true vocal cords, thin strips of cartilage that vibrate together to produce sound. It is protected in the front by the large thyroid cartilage, which can be felt as the "Adam's apple" in our neck. When you feel for your Adam's apple, directly under that large piece of firm cartilage is the voice box, or the glottic portion of the larynx where the true vocal cords are located. Directly above the actual voice box is the supraglottic larynx, or supraglottis. This area contains some of the lining of the throat, cartilage and muscles that control the movement of the vocal cords, and the epiglottis, which is a flap of cartilage that closes over the voice box to protect our airway during swallowing. Below the vocal cords is the subglottic larynx, or subglottis. This area is the area of the throat and airway below the vocal cords but above the trachea. All three of these areas together are considered the larynx.

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What is laryngeal cancer?

The definition of a tumor is a mass of abnormally growing cells. Tumors can be either benign or malignant. Benign tumors have uncontrolled cell growth, but without any invasion into normal tissues and without any spread. A tumor is called malignant (cancer) when tumor cells gain the propensity to invade tissues and spread locally as well as to distant parts of the body. In this sense, laryngeal cancer occurs when cells in the lining of the throat grow uncontrollably and form tumors that can invade normal tissues and spread to other parts of the body.

Cancers are described by the types of cells from which they arise. Over 95% of laryngeal cancers arise from the lining of the throat (not from the actual muscle or cartilage cells) and are called squamous cell carcinomas. Approximately 5% of these are called verrucous carcinoma, which have a wart-like appearance to them and are often less aggressive and slow-growing. Although there are other cancers that can arise in the larynx (salivary gland tumors-from minor salivary glands contained in the larynx, lymphomas of the larynx, and sarcomas-from muscle and cartilage cells), the vast majority are squamous cell carcinomas. Hence, these are the most commonly studied.

In addition to invasive cancers, patients are sometimes diagnosed with precancerous lesions, called carcinoma-in-situ. These most commonly occur in the glottis itself (where the true vocals cords are), as this area is more likely to produce early signs of disease. Carcinoma-in-situ occurs when the lining of the throat undergoes changes similar to cancerous changes without any invasion into the deeper tissues. Hence, while the cells themselves have cancer-like qualities, there is no risk of spread, as no invasion has occurred.

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Am I at risk for laryngeal cancer?

Laryngeal cancer occurs in approximately 12,000 Americans per year, causing about 4,200 deaths. It makes up one quarter to one third of all cancers of the throat. It has classically been thought of as a disease that affects older men.

Although the exact cause of larynx cancer is unknown, certain factors increase the risk of developing cancer of the larynx, including:
  • Age: While larynx cancer can strike at any age, it is most often diagnosed in people over the age of 50.
  • Ethnicity: Cancer of the larynx is more common in Africa-Americans than in other ethnic groups.
  • Gender: Men are four to 10 times more likely to develop larynx cancer than women.
  • Lifestyle: Both smoking and excessive alcohol use increase the risk of larynx cancer. The risk becomes even higher if a person both smokes and drinks heavily. Similarly, people who work with asbestos, sulfuric acid or nickel have a greater than normal risk of developing cancer of the larynx. As a result, if you have an occupation that continually exposes you to these carcinogenic materials, be sure to follow all safety precautions to lower their risk of exposure.
  • Occupation: Larynx is not one of the cancer sites strongly linked with occupation. Some exposures in the workplace may make a small contribution to risk, although evidence in many cases remains conflicting. Occupational exposure to coal dust has been shown in one study to increase laryngeal cancer risk, with a risk ratio of more than six for the most highly exposed.
  • Medical history:
    • A previous history of head or neck cancer greatly increases the risk of larynx cancer.
    • Some studies also suggest that gastroesophageal reflux disease, or GERD, increases the risk of larynx cancer.
    • almost three-fold increased risk of laryngeal cancer in people with HIV/AIDS and a two-fold risk increase in transplant recipients, suggesting a role of immunosuppression in the disease.
    • An increased risk of laryngeal cancer has been shown for people with evidence of human papillomavirus-16 infection in the larynx (up to 19-fold risk increase), or in blood samples (up to a three-fold risk increase).

Smoking and Alcohol Consumption

Many risk factors have been implicated in the development of laryngeal cancer. These include chronic irritation from laryngitis or voice abuse, chronic gastric reflux, and exposure to certain chemicals, such as wood dust, nitrogen mustard, and asbestos. However, far and away the largest risk factor for the development of laryngeal cancer is smoking. Pipe smoking, cigar smoking, and cigarette smoking have all been strongly associated with the development of larynx cancer. There is also an association between heavy alcohol intake and laryngeal cancer. Although it has classically been thought of as a co-risk factor that only increases the risk of smoking, some more recent studies have shown that heavy alcohol use can increase the risk of laryngeal cancer by itself. It is estimated that heavy drinking increases the risk of laryngeal cancer by 2-6 times, while smoking increases the risk between 5-35 times, depending on how much one smokes.

Tobacco use is measured in pack-years, where one pack per day for one year is considered one pack-year. Two pack-years is defined as either one pack per day for two years, or two packs per day for one year (Longer terms of pack years are determined using a similar ratio.) Depending upon the number of pack-years smoked, studies have reported that smokers are about 5 to 35 times more likely to develop laryngeal cancer than non-smokers. It does seem that the duration of tobacco exposure is probably more important overall to cancer causing effect, than the intensity of the exposure.

In a person who both smokes and drinks, the risk is increased to up to 40 times the risk of someone who neither smokes nor drinks. National public health measures have been implemented in the United States to attempt to decrease the abuse of tobacco and alcohol. Although no specific decrease has been seen yet, there is hope that these measures will lead to a decrease in the incidence of laryngeal cancers over the next 15 years.

Though there is some improvement in the smoking rates in younger people in the United States, there is still a large proportion using smokeless tobacco. This puts them at a higher risk of oral cavity, tongue, and lip cancer. People who use smokeless tobacco may also be at increased risk for developing cancer of the supraglottic larynx, although this risk is probably not as high as it is for people who smoke cigarettes, cigars, or a pipe.

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How can I prevent laryngeal cancer?

Smoking is by far the strongest risk factor associated with the development of laryngeal cancer. Since it is fairly uncommon for a non-smoker to be diagnosed with laryngeal cancer, smoking cessation is the best way to prevent laryngeal cancer. In fact, not using tobacco of any kind, by either smoking or smokeless, is the healthiest thing anyone can do, both in terms of preventing laryngeal cancer, as well as the prevention of other throat cancers, lung cancers, and many other serious health problems.

Reducing alcohol intake may also be helpful in the prevention of laryngeal cancer, especially for people who smoke. Reducing other risk factors, such as chronic vocal irritation and gastroesophageal reflux may also be beneficial. A healthcare professional should be consulted for chronic health problems such as laryngitis or chronic heartburn.

Trials have been performed in the past investigating 13-cis-retinoic acid (found in vitamin A) for the prevention of second cancers after patients were cured of their first cancer. There was a large decrease in the incidence of these second cancers in patients who used 13-cis-retinoic acid. However, this has not yet been substantiated and is currently being tested in patients without a history of cancers. Regardless of the outcome, taking 13-cis-retinoic acid is by no means a substitute for smoking cessation.

What screening tests are available?

Cancer of the larynx affects about 15,000 people per year, which is many fewer than breast cancer, lung cancer, and prostate cancer. Therefore, it is not large enough of a health problem to warrant screening of the general population. Some physicians have advocated screening in high-risk patients (heavy smokers), though screening program have not been proven to be beneficial, even in this population.

Hoarseness is often an early sign of laryngeal cancer; especially in cancer of the true vocal cords. Therefore, physicians should regularly screen their patients for complaints of hoarseness or changes in their voice quality and patients should bring the attention of their physicians to these symptoms. In these cases, patients should be referred to an otolaryngologist (an ear-nose-throat doctor) for evaluation. The laryngeal cancer detection rate in these situations is usually between 3-5%.

What are the signs of laryngeal cancer?

Signs or symptoms of larynx cancer are somewhat dependent on where the cancer is growing (supraglottis, glottis, subglottis). Patients with glottic cancer, or cancer that grows on the true vocal cords, often present with the early sign of hoarseness. This occurs because even a slight interference with the vibrating function of the vocal cords can produce voice changes. Hence, any long-standing hoarseness or voice changes should prompt a laryngeal examination. If hoarseness is ignored or if advanced disease occurs, airway obstruction, pain, or difficulty swallowing can result.

Supraglottic cancers usually do not produce early signs or symptoms, so supraglottic cancers are more often in advanced stage upon diagnosis. Hoarseness can also occur with supraglottic cancer, though usually later in the disease state. Also, in patients with supraglottic cancer, voice changes referred to as "hot potato voice" can occur. This can be described as the type of voice someone would speak in if they had a piece of hot food (potato) in their mouth. In addition to voice changes, patients can also present with pain, problems swallowing, or even ear pain, which can result from the involvement of nerves in the throat by the tumor. Supraglottic cancers often spread to lymph nodes in the neck, and many patients notice a lump in the neck as the first sign of cancer. Any lump or bump in the neck that does not go away within a few days should be evaluated by a physician.

Subglottic cancers are fairly rare, though they also fail to produce early symptoms. Therefore, they also present in more advanced stages and patients can have signs of disease similar to that of supraglottic cancers.

Again, these signs and symptoms are nonspecific and could represent a variety of different conditions-both benign and malignant. However, if you have any of these symptoms, especially if they are longstanding or if you are a smoker, you should see your physician.

Diagnosis

If you have symptoms of cancer of the larynx, the doctor may do some or all of the following exams:
  • Physical exam. The doctor will feel your neck and check your thyroid, larynx, and lymph nodes for abnormal lumps or swelling. To see your throat, the doctor may press down on your tongue.
  • Indirect laryngoscopy. The doctor looks down your throat using a small, long-handled mirror to check for abnormal areas and to see if your vocal cords move as they should. This test does not hurt. The doctor may spray a local anesthesia in your throat to keep you from gagging. This exam is done in the doctor's office.
  • Direct laryngoscopy. The doctor inserts a thin, lighted tube called a laryngoscope through your nose or mouth. As the tube goes down your throat, the doctor can look at areas that cannot be seen with a mirror. A local anesthetic eases discomfort and prevents gagging. You may also receive a mild sedative to help you relax. Sometimes the doctor uses general anesthesia to put a person to sleep. This exam may be done in a doctor's office, an outpatient clinic, or a hospital.
  • CT scan. An x-ray machine linked to a computer takes a series of detailed pictures of the neck area. You may receive an injection of a special dye so your larynx shows up clearly in the pictures. From the CT scan, the doctor may see tumors in your larynx or elsewhere in your neck.
  • Biopsy. If an exam shows an abnormal area, the doctor may remove a small sample of tissue. Removing tissue to look for cancer cells is called a biopsy. For a biopsy, you receive local or general anesthesia, and the doctor removes tissue samples through a laryngoscope. A pathologist then looks at the tissue under a microscope to check for cancer cells. A biopsy is the only sure way to know if a tumor is cancerous.


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