About Mesothelioma
Mesothelioma is a cancer that affects the mesothelium, the protective
lining that covers most of the internal organs. The specific name of the
mesothelium varies depending on which organ it cushions and protects.
Mesothelioma can affect the mesethelium of one organ or of many. The most common types of mesothelioma affect the peritoneum, which lines the abdominal cavity, and the pleura, which covers the lungs. In the body of a mesothelioma patient, the cells of the mesothelium begin to divide and multiply abnormally. Left unchecked, these cancer cells can invade other organs.
In the United States, only about 2,000 new cases are diagnosed annually, making mesotheloima a rare cancer. The occurrence of the disease has been increasing over past decades, but it is still an uncommon disease. Men develop mesothelioma more often than women do, but neither gender is immune.
Who is at risk
People who work in industries in which they are exposed to asbestos
fibers run the greatest risk of developing the disease. Asbestos is a
mineral that naturally occurs in long, thin fibers that can easily
become airborne. It has been used in this country since the 1880s
because it is resistant to heat, electricity, and chemicals, and it
absorbs sound as well. Before knowledge of its toxic properties became
widespread, asbestos was used in insulation and fire-retardant
materials, so asbestos mining was a relatively common and profitable
business in many different parts of the United States. Since the 1980s,
many countries have banned the use of asbestos in manufacturing.
Asbestos exposure accounts for as much as 80 percent of all mesthelioma cases. As a person’s exposure to asbestos increases, the chances that s/he will develop the disease likewise rise, though some mesothelioma patients appear not to have been exposed to the carcinogen at all. Exposure to asbestos is also known to cause other diseases, including lung cancer and asbestosis.
In some cases, people who live with others who work in such industries are also at risk, if they are exposed to asbestos by handling the contaminated clothing or personal effects of their cohabitant, or if long, thin asbestos fibers become airborne and they inhale the carcinogen. Thus it is also possible that people who live near companies that have manufactured or used asbestos also can be exposed to the carcinogen.
Furthermore, many older homes were built using materials, including electrical wiring and other insulated elements, that contained asbestos, so people who live in or remodel such houses risk asbestos exposure.
Smoking is not a risk factor per se for mesothelioma, but individuals who develop the disease and also smoke are at greater risk of developing cancer of the lungs and windpipe.
How exposure to asbestos causes mesothelioma
The most common way that asbestos fibers infiltrate the body is by being inhaled into the lungs and then spread throughout the body via the lymphatic system. In some cases, asbestos has been ingested, which passes it into the digestive tract. In any event, the asbestos typically then migrates to other internal organs. Research seems to suggest that asbestos is a direct carcinogen, meaning that exposure to it causes cancerous mutations of the cells. There is also some evidence that asbestos can produce abnormalities in the body’s chromosomes, which control the replication of cells.
How mesothelioma is diagnosed
Unfortunately, the symptoms of mesothelioma are quite commonly caused by
many other illnesses. In the case of mesothelioma of the pleura, the
patient may experience chest pain and shortness of breath, caused by
accumulating fluid in the chest cavity. Mesothelioma of the peritoneum
causes weight loss, abdominal pain, and fluid build-up in the belly. If
the cancer spreads, it can cause a myriad of symptoms throughout the
body.
Because the disease can affect the mesothelium in any part of the body, and because the symptoms can resemble those caused by any number of other ailments, diagnosis can be difficult. A physician usually starts by taking the patient’s medical and employment history and then proceeding to a complete physical examination. The patient may be subjected to a CAT scan and/or an MRI, both of which procedures produce images of the internal organs that the doctor can then examine. If s/he suspects the patient has mesothelioma, the doctor usually will order a biopsy, which will be examined by a pathologist to see if cancer cells are present.
Once the diagnosis has been confirmed, the doctor will determine what stage the cancer is in, and whether it is localized (limited to a specific membrane) or has spread to other parts of the body. This information becomes the basis for the physician’s plan to treat the patient.
How mesothelioma is treated
Treatment of this disease usually involves surgery, radiation therapy,
chemotherapy, or, most commonly, a combination of these therapies. If
the physician decides surgery is warranted, the affected lining and
sometimes adjacent organs are removed. Radiation therapy can be useful
because it narrowly targets the cancerous area while avoiding damaging
other parts of the body. Chemotherapy relies on anticancer drugs,
generally administered intravenously, to kill off cancer cells. All of
these therapies have significant risks as well as benefits, and can
trigger side effects as well.
Research into treatment of mesothelioma is ongoing, and clinical trials of new therapies are underway at many major cancer centers. For more information on clinical trials, consult the National Cancer Institute’s website at http://www.cancer.gov/clinicaltrials.
The prognosis for patients diagnosed with mesothelioma
Statistics published by the American Cancer Society indicate that the five-year survival rate for patients with mesothelioma is about 10 percent. Many newly diagnosed patients are told they can expect to live only another year or less. This low survival rate is at least partly a reflection of the fact that many patients aren’t diagnosed until the cancer is advanced. Still, treatment can slow the progress of the disease, and some people have lived for decades after being diagnosed.