Mesothelioma is a rare form of cancer that attacks the cells of the mesothelium, a thin membrane that lines the thoracic and abdominal cavities as well as the heart sac. It has been determined that the cause of mesothelioma is almost always exposure to asbestos. This disease is one of the most aggressive forms of cancer and there is no known mesothelioma cure. Unfortunately, most patients die within just a few years of a mesothelioma diagnosis.
Mesothelioma cancer was first described and recognized as a pathologic entity in the 1870s by E. Wagner, who found two cases during a study of some 3,000 autopsies. However, this form of cancer was not recognized as a separate form of lung cancer until almost 100 years later. In 1960, a report by Wagner et al finally established asbestos as a definitive cause of the disease, citing a study of 30 cases of mesothelioma in South Africa, including those who were exposed on their jobs as miners and others with simply passing exposure. By just a few years later, the British Journal of Industrial Medicine confirmed that miners as well as those who lived near asbestos mines but didn’t work in mining were both developing the disease. Many similar reports followed.
Asbestos and Mesothelioma
As studies continued to point to asbestos as one of the primary mesothelioma causes, it became more and more evident that this mineral was wreaking havoc with the lungs of those who were consistently exposed to it. A close look at asbestos, its types, and its uses would soon prove necessary in the study of mesothelioma disease.
Asbestos comes in a variety of shapes and sizes. Some types of asbestos are more lethal than others. As a matter of fact, the types of asbestos that belong to the amphibole group are the most toxic. These include amosite, tremolite, crocidolite, actinolite, and anthophyllite asbestos. The fibers that make up these amphibole varieties are long, thin, and sharp. Once inhaled, they are difficult to expel and become imbedded in the chest area where they cause scarring and can eventually result in the development of cancerous tumors and mesothelioma disease.
The serpentine form of asbestos - known as chrysotile - has been proven to be less likely to cause cancer but is hazardous nonetheless. Experts advise that any kind of asbestos exposure is unsafe and there have indeed been cases when chrysotile fibers were found in the lungs of those with mesothelioma disease.
Asbestos has been mined for centuries, but the mineral, long considered a prime insulating material, enjoyed increased use after the Industrial Revolution. In particular, peak usage of this hazardous mineral occurred from the 1930s through the 1970s, and asbestos use was especially popular during World War II, particularly in the shipbuilding industry.
A total of about 90% of all patients who develop mesothelioma disease are believed to have been exposed to asbestos in the workplace. Navy vets and shipyard workers account for about one-third of these cases, putting them in the highest risk group for developing this aggressive cancer. Furthermore, in 1978, a study found that the disease affects 6% of workers who have been employed in high-risk occupations at asbestos jobsites for 15 years or longer, confirming that length of exposure may also have something to do with who gets asbestos and who does not.
Recent events have also shown that exposure to a large amount of asbestos for a short amount of time may also result in development of this disease. For example, emergency responders who worked at the World Trade Center disaster were diagnosed with pleural mesothelioma or peritoneal mesothelioma within just a few short years of being exposed to the material in the days surrounding 9/11. The first Sept. 11-related victim of the disease died in 2005, just four years after the tragedy occurred.
Individuals may also suffer secondhand exposure to asbestos. In 1990, for example, researchers discovered that half the mesothelioma patients under the age of 40 were exposed to asbestos in childhood. Many grew up in the shadow of an asbestos plant or mine, some lived near a natural source, and others had family members who worked with asbestos and inadvertently brought fibers into the home on their clothes, skin, or in their hair.
Today, the average mesothelioma patient is a white male, 65 years of age or older. However, this statistic has more to do with employment than with specific mesothelioma risk factors. In addition, researchers have studied the impact of certain genetic factors on the development of mesothelioma and note that those with a family history of cancer have a greater chance of developing mesothelioma. This may explain why some individuals with only minimal exposure develop the disease.
Regardless of how and why an individual develops mesothelioma disease, doctors acknowledge that it is one of the most difficult cancers to treat. The disease has a long latency period, remaining essentially silent for up to five decades. Because it is usually not diagnosed until it has reached advanced mesothelioma stages, most standard treatments for cancer are not very effective in slowing the disease, adding only a few months to the patient’s life expectancy. However, some newer treatments such as mesothelioma gene therapy and photodynamic therapy have shown promise in fighting this cancer and tests are being developed that will help detect the disease at an earlier stage, providing more hope for the mesothelioma patient.
Wagner JC, Sleggs CA, Marchand P (October 1960). "Diffuse pleural mesothelioma and asbestos exposure in the North Western Cape Province". Br J Ind Med. 17: 260-71.