of Malignant Mesothelioma
Information about the prevention of cancer and the science of screening appropriate individuals at high-risk of developing cancer is gaining interest. Physicians and individuals alike recognize that the best “treatment” of cancer is preventing its occurrence in the first place or detecting it early when it may be most treatable.
The chance of an individual developing cancer depends on both genetic and non-genetic factors. A genetic factor is an inherited, unchangeable trait, while a non-genetic factor is a variable in a person’s environment, which can often be changed. Non-genetic factors may include smoking, diet, exercise, or exposure to other substances present in our surroundings. These non-genetic factors are often referred to as environmental factors. Some non-genetic factors play a role in facilitating the process of healthy cells turning cancerous (i.e. the correlation between smoking and lung cancer) while other cancers have no known environmental correlation but are known to have a genetic predisposition. A genetic predisposition means that a person may be at higher risk for a certain cancer if a family member has that type of cancer.
Heredity or Genetic Factors
There does not appear to be a hereditary risk for individuals developing mesothelioma
Environmental or Non-Genetic Factors
Mesothelioma is primarily associated with environmental factors, especially exposure to asbestos and smoking.1
Asbestos: Asbestos is the general name applied to a group of naturally occurring minerals that form fibers. These asbestos fibers have been used in a variety of applications such as textiles, cement, paper, wicks, ropes, floor and roofing tiles, water pipes, wallboard, fireproof clothing, gaskets and brake linings.
Asbestos fibers easily break into particles. When inhaled, these dust particles can lodge in the lungs and cause damage that leads to an increased risk of lung cancer. It is estimated that since the beginning of World War II, approximately 8 million people have been exposed to asbestos in the workplace. Approximately 5% of the lung cancer cases diagnosed each year are caused by asbestos.
Asbestos increases the risk of developing mesothelioma. Mesothelioma can result from neighborhood or environmental exposure to asbestos, occupational exposure, and household contact with asbestos dust. The rates of mesothelioma peaked for individuals born around 1910 and have steadily declined over time. Currently, there are about 2,000 cases of mesothelioma each year. This is primarily an asbestos-related cancer; only a fraction of mesothelioma cases are unrelated to asbestos exposure. Individuals involved in shipbuilding during World War II have an increased risk of mesothelioma. In fact, several shipbuilding areas such as Virginia, England, Wales and Japan, have higher rates of mesothelioma. In addition, workers who are heavily exposed to asbestos bring the dust into their homes on their clothing, hair and skin, thus exposing their family members and placing them at a higher risk of developing mesothelioma. Smoking does not appear to increase the risk of developing mesothelioma.
Clinical studies have demonstrated that individuals who are exposed to large amounts of asbestos have a 5 times greater chance of developing lung cancer than individuals who have not been exposed.
Cigarettes: Individuals who smoke and are exposed to asbestos have an even greater risk of developing mesothelioma. Studies show that smokers who are exposed to asbestos are 90 times more likely to develop lung cancer than individuals who do not smoke and have not been exposed to asbestos.
There is also large body of research that indicates that individuals who smoke are at a significantly increased risk of developing lung cancer. Approximately 85% of the lung cancer cases diagnosed each year can be associated with smoking. Over time, carcinogens in cigarettes damage the cells in the lungs and eventually, these damaged cells may become cancerous. Several factors contribute to a smoker’s risk of developing lung cancer, such as the age at initiation of smoking, the number of years smoked, the depth of inhalation, and the number of cigarettes smoked daily.
Cigars and Pipes: Individuals who smoke cigars or pipes appear to be at an increased risk of developing lung cancer, although this risk appears lower than that of cigarette smokers. Again, the number of years smoked, the amount smoked and the depth of inhalation all play a role in whether or not lung cancer will develop. Researchers have speculated that the reason for the decreased risk among cigar and pipe smokers when compared with cigarette smokers may be that cigar and pipe smokers do not inhale as deeply as cigarette smokers because cigar smoke tends to be more irritating. Cigar smokers also tend to smoke less each day, as it takes about 1-2 hours to completely smoke a cigar, whereas it takes less than 10 minutes to smoke a cigarette.
Radon: Radon is a carcinogen that can cause damage to the lungs that may eventually lead to lung cancer. It is estimated that radon is responsible for about 10% of the lung cancer cases diagnosed each year. Individuals who smoke and are exposed to radon are at an even higher increased risk of developing lung cancer. Most of the cancer deaths associated with radon occur among smokers.
Radon is a naturally occurring, invisible radioactive gas. It is present in soil and rocks and can seep into homes and other buildings. In situations where ventilation is restricted, radon can accumulate in the atmosphere and lead to higher levels of exposure. Individuals who work in mines are often exposed to higher concentrations of radon than the general population. However, radon can also be present in many homes. Some geographic areas have higher concentrations of radon, but radon can also seep into homes in geographic areas that are not considered high risk. When ventilation is restricted in basements in order to conserve energy, radon can seep from the soil into the basement and accumulate in the poorly ventilated area.
Cancer is largely a preventable illness. Two-thirds of cancer deaths in the U.S. can be linked to tobacco use, poor diet, obesity, and lack of exercise. All of these factors can be modified. Nevertheless, an awareness of the opportunity to prevent cancer through changes in lifestyle is still under-appreciated.
Nearly everyone has been exposed to asbestos at some point. Asbestos is widely used and small amounts may be found in a variety of products. In addition, the breakdown of asbestos products as well as natural deposits of the fiber can cause the release of asbestos particles into the environment.
Three agencies are responsible for regulating the use of asbestos products and the exposure caused to the general public. The Environmental Protection Agency (EPA) regulates asbestos in buildings, drinking water and the environment. The Consumer Product Safety Commission (CPSC) regulates asbestos in consumer products. The Food and Drug Administration (FDA) monitors asbestos contamination in food, drugs and cosmetics.
Still, individuals may be exposed to asbestos at work or in other environments. The Occupational Safety and Health Administration (OSHA) has issued regulations for employers regarding the treatment of asbestos exposure in the workplace. In addition, the Mine Safety and Health Administration (MSHA) regulates mine safety. Often, workers are provided with protective equipment and instructions regarding work practices and safety procedures. Individuals concerned about asbestos exposure at work may wish to discuss safety precautions with their employers or request information from OSHA. Individuals who are or have been exposed to asbestos should refrain from smoking.
Screening and Early Detection
For many types of cancer, progress in the areas of cancer screening and treatment has offered promise for earlier detection and higher cure rates. The term screening refers to the regular use of certain examinations or tests in persons who do not have any symptoms of a cancer but are at high risk for that cancer.
Several key organizations now recommend screening for lung cancer with helical low-dose computed tomography (LDCT) for selected patients at high risk of developing the cancer.
These recommendations were largely based on results from The National Lung Screening Trial (NLST). The NLST enrolled current and former heavy smokers and screened them annually with either chest x-rays or low-dose spiral CT. People in the CT group were 20% less likely to die of lung cancer.
Low-dose CT scans are a special type of imaging scan that can identify smaller nodules than chest x-rays, making them a strong candidate for lung cancer screening. Although low-dose CT scans can detect lung cancer early, they also can have false-positive results, which means they may not be appropriate for standard use because false-positive results can lead to unnecessary invasive procedures that can have deadly complications. However, in high-risk populations—such as older individuals who are current or former smokers—the benefits of screening with low-dose CT scans appears to outweigh the harms.
The guidelines recommend that smokers and former smokers ages 55 to 74 who have smoked for 30 pack years or more and either continue to smoke or have quit within the past 15 years should undergo annual screening with low-dose CT scan.2,3
1 Antman KH, Pass HI, DeLaney T, et al. Benign and malignant mesothelioma. In: Devita VT Jr, Hellman S, Rosenberg SA, eds. Cancer Principles and Practice of Oncology. 4th Edition Philadelphia, PA:JB Lippincott Co;1993:1489-1508.
2 Ruffie P, Feld R, Minkin S, et al. Diffuse Malignant Mesothelioma of the Pleura in Ontario and Quebec: A Retrospective Study of 332 Patients. Journal of Clinical Oncology 1989;7:1168-1168.