Laryngeal cancer is a relatively rare disease that affects the larynx, more commonly known as the voice box or Adam's apple. The leading risk factors for cancers of the larynx are smoking and excessive alcohol consumption. Workplace exposure to asbestos is also linked to the development of this type of cancer.
Past investigations of the link between asbestos and laryngeal cancer were somewhat contradictory. However, a 2006 report sponsored by the National Institutes of Health confirmed the connection.
The report found that asbestos not only was determined to be a definite cause of laryngeal cancer, but also found that the cancer risk was dependent on the amount of exposure. This means the risk of developing the disease increases with the duration and extent of asbestos exposure.
For decades, researchers have attempted to confirm a definitive link between asbestos exposure and the development of laryngeal cancer — often with mixed results. Some studies find no significant increase in cancer risk.
Other studies show elevated risk among asbestos-exposed workers, but failed to consider the test subjects' smoking and alcohol consumption history. Because these are both critical risk factors for laryngeal cancer, the oversight likely exaggerated previous data on the true asbestos risk.
In an effort to draft laws to compensate asbestos-exposed workers fairly, the U.S. Senate Committee on the Judiciary formed the Committee on Asbestos: Selected Health Effects. With sponsorship from the National Institutes of Health, the committee explored a wide range of adverse health effects potentially caused by asbestos, including laryngeal cancer. The study, "Asbestos: Selected Cancers," was published in 2006.
The Committee on Asbestos reviewed 35 cohort studies and 18 case-control studies related to laryngeal cancer, taking the subjects' smoking and drinking histories into careful consideration. The subject group was comprised of patients who were exposed to asbestos in a variety of occupations throughout North America, South America, Europe and Japan.
The committee discovered that compared to workers who reported no past exposure, the risk of laryngeal cancer for asbestos-exposed workers was increased by 40 percent in the cohort studies and 43 percent in the case-control studies. Among the most highly exposed subjects, the increase in cancer risk ranged from 38 percent to 157 percent.
In all nine of the largest cohort studies and both the cohort and case-control combined analyses, asbestos exposure was found to significantly increase the risk of laryngeal cancer. In the highest exposed workers, the chances of developing laryngeal cancer were more than double that of workers not exposed to asbestos.
The studies established a sufficient link between asbestos and laryngeal cancer and stated that the risk is dose-dependent. Therefore, as the intensity, duration or likelihood of asbestos exposure increased, so did the risk of developing laryngeal cancer.
It is well-established that cancers like mesothelioma and lung cancer develop once airborne asbestos fibers are inhaled and begin to accumulate in the lungs. Because asbestos must pass through the larynx before it reaches the lungs, fibers can penetrate laryngeal tissue and collect there as well.
Cancers are often classified by histological type, or the structure and makeup of their cells. The majority of laryngeal cancers arise in the squamous cells of the upper airway. This type of cell has a flat scale-like appearance and forms a protective layer around several locations throughout the body. When these cells become cancerous, they are called squamous cell carcinomas.
Like the squamous cell carcinomas that develop in the skin, digestive track and lungs, squamous cell carcinomas of the larynx form gradually as healthy cells mutate into increasingly abnormal clones. When asbestos fibers penetrate the larynx, they cause genetic changes and cells begin to divide uncontrollably.
Studies have shown that smoking and drinking, either alone or in combination, can contribute to the buildup of asbestos in the lining of the larynx. Tobacco smoke may cause laryngeal damage while theoretically increasing the potential for asbestos fibers to become lodged in the trachea, which connects the larynx to the lungs.
Heavy consumption of alcohol intensifies this effect and can lead to chronic irritation or inflammation that speeds up the development of abnormal cell growth. Heavy smoking and drinking can cause the vocal cords to become inflamed or damaged, which may disrupt airflow and increase a person's susceptibility to asbestos buildup in the throat.
If you've been exposed to asbestos, make sure to receive annual screenings to check for signs of asbestos-related disease. Catching asbestos-caused conditions early on affords the best and most effective treatment options.
The signs of laryngeal cancer are often noticeable early on, which makes treatment fast and effective. Vocal changes like hoarseness are easy to recognize. Visible signs of disease, such as small tumor masses on the vocal cords, can also lead to early diagnoses. Average survival rates for laryngeal cancer are impressive because early diagnosis and treatment often translates to high success rates.
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