Mesothelioma is a terminal type of cancer with no known cure. Although some patients live much longer, the average survival rate at the time of being diagnosed with malignant mesothelioma is around 4 to 18 months. The number one cause of mesothelioma is exposure to asbestos, which is a naturally occurring mineral and known carcinogen that was widely used in consumer products and building materials until about the 1980s. However, asbestos is not the only established cause of mesothelioma.
Asbestos is the number one cause of mesothelioma and the main risk factor. In most cases, mesothelioma stems from prolonged exposure to asbestos, such as people who work around asbestos daily. However, statistics surrounding mesothelioma diagnoses find that only around 70 to 80 percent of patients who are diagnosed with pleural mesothelioma (the most common type) have a history of asbestos exposure. The other 20 to 30 percent of patients do not report having been exposed to asbestos.
In addition, about half of all documented cases of peritoneal mesothelioma have occurred in patients with no known history of asbestos exposure – mainly, women. This could potentially be explained away with secondhand exposure. This occurs when someone in a worker’s home, such as a worker’s wife, is exposed to asbestos fibers from the worker’s clothing. Yet, while it is rare, there are documented cases of patients getting mesothelioma without having been exposed to asbestos at all.
One environmental exposure hazard that has been connected to mesothelioma besides asbestos is erionite. Erionite is a fibrous volcanic mineral that falls under the mineral group zeolites, which are chemically related to asbestos. In the United States, erionite is found mainly in the Western states and North Dakota. Workers may be exposed to erionite in road development projects and rock quarries. Exposure to erionite can cause mesothelioma through the same mechanics as asbestos.
Other researchers believe that exposure to radiation, certain chemicals and viruses could lead to the development of mesothelioma in a patient. For example, in the past, researchers alleged that the simian virus 40 (SV40) was linked to some cases of mesothelioma; although this research has been largely discredited due to the possibility of false negative tests using the polymerase chain reaction testing technique. The link between these causative agents and the development of mesothelioma is not well understood.
Like most cancers, mesothelioma arises from a combination of an individual’s genetics and environmental exposures – not the environmental exposure alone. The genetic factor may be why some people can be exposed to asbestos regularly and still not develop malignant tumors while others can be exposed just once and get mesothelioma.
Inherited mutations of certain genes – such as the tumor suppressing gene BAP1 – may result in a genetic predisposition to developing mesothelioma. It is possible that a person who is genetically predisposed to mesothelioma may not develop this disease unless there is a loss of the second copy of the gene. This loss could be triggered due to certain environmental factors, such as the radiation or viruses mentioned above.
While the majority of patients trace their illnesses back to a time in their lives when they were exposed to asbestos, such as on the job or in the military, some are diagnosed with spontaneous (idiopathic) mesothelioma. This means that the cause of the mesothelioma is unknown or uncertain. This only occurs in about one patient per million, however. While it is possible that the patient may be unaware that he or she was exposed to asbestos, the cause could also be related to other factors.
There is still much to be understood about mesothelioma. Scientists and researchers are constantly striving to learn more about asbestos and its effects on the human body, as well as to search for a cure for mesothelioma.