Pleural Mesothelioma: An Overview
Pleural mesothelioma is by far the most prevalent form of mesothelioma. According to the American Cancer Society, three-quarters of all mesothelioma cases are pleural mesothelioma. The number of total mesothelioma cases in the United States increased between 1970 and 1990. This number has stabilized and seems to be on the decline, as fewer people are now exposed to asbestos at their workplace. The rate of mesothelioma cases in Europe is still increasing and there has been speculation and estimates that the rate could also increase in the United States.
Asbestos-The Primary Cause
Inhaling asbestos fibers is the primary cause of pleural mesothelioma. Other factors such as genetics, smoking, and exposure to the simian virus (which contaminated some older polio vaccines) may predispose some people to develop mesothelioma when exposed to asbestos. Some individuals exposed to asbestos for a prolonged period do not develop mesothelioma or asbestosis.
Asbestos is a naturally occurring mineral that was widely used in various industries and construction because of its fire-retarding and insulating properties. Since the 1980s, its use in industry and consumer products has been more regulated and some U.S. legislators would like to ban it entirely.
Serpentine and amphiboles are the two main forms of asbestos. Chrysotile asbestos, which is most commonly used in commercial products, is the only type of serpentine. Amphiboles are divided into five main types: actinolite, amosite, anthrophyllite, crocidolite, and tremolite.
Serpentine fibers are flexible and curly. Amphiboles have long, thin fibers and are thought to be a greater cancer risk than serpentine fibers, but exposure to either serpentine or amphibole asbestos is dangerous.
How Asbestos Exposure Occurs
People who worked for an extended period of time in an environment where asbestos dust was regularly released are at greatest risk for pleural mesothelioma. The body's natural defense mechanisms successfully clear many asbestos fibers, but when asbestos exposure is heavy, these defense systems are overwhelmed. Mucus within the airways traps asbestos fibers and other toxins that are inhaled. These trapped foreign particles are either swallowed or coughed up.
Some asbestos fibers are difficult for the body to rid itself of. These long, pointed fibers can reach the pleural lining of the chest wall and lung. Once the fibers have penetrated the pleura they injure the mesothelial cells. Researchers are uncertain exactly how this injury leads to cancerous changes.
The tissue changes leading to mesothelioma occur slowly. The symptoms of mesothelioma generally do not appear for 20 to 30 years after the initial asbestos exposure. A latency period of up to 50 years has been known.
Symptoms and Treatment
Pleural mesothelioma is a difficult cancer to treat because its symptoms do not appear until it is well advanced. It is frequently not diagnosed until it is the advanced stages. The symptoms of pleural mesothelioma are similar to many other illnesses and include shortness of breath, coughing, and chest pain.
Treatment options for pleural mesothelioma include surgery, chemotherapy, and radiation. Multimodal (combination) treatment including all three of these options has worked well for some otherwise healthy people in the early stage of pleural mesothelioma. Frequently, treatment for mesothelioma is aimed at relieving symptoms, rather than curing the disease. New treatment options are being tested in clinical trials and many are leading to promising findings.
Resources
The American Cancer Society
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Center for Cancer Research
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Livestrong
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CDC | Cancer Prevention
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CanCare, Inc.
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