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Asbestos-Related Cancers

While the causal relationship between asbestos exposure and mesothelioma cancer is well known, there are other asbestos-related cancers that affect thousands of people in the United States every year. An asbestos-related cancer is any cancer caused by asbestos exposure, and most cases are caused by occupational contact with the toxic mineral. Mesothelioma and lung cancer have a confirmed connection to asbestos, while others like gastrointestinal cancer have an association with asbestos but more research is required before a full causal relationship is confirmed. 

In addition to mesothelioma, three other cancers are medically proven to be caused by asbestos exposure, including lung cancer, ovarian cancer and laryngeal cancer. Gastrointestinal and colorectal cancers have an association with asbestos exposure, but a direct causal relationship has not been officially established for these cancers. Additionally, there is an elevated risk of esophageal, throat, kidney and gallbladder cancer among those exposed to asbestos, but studies have been inconclusive on these cancers.

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Confirmed Asbestos-Related Cancers

In order for a cancer to have a causal relationship with asbestos exposure, numerous studies and medical research is needed to confirm a direct connection between the two. Most studies evaluate the incidence rate of a cancer in workers of a particular occupational setting known for asbestos exposure, such as insulation, factory and labor workers. If a large enough amount of asbestos-exposed workers are found to develop a specific cancer in multiple studies, then more studies are conducted to investigate a causal relationship. The following four confirmed asbestos-related cancers are most often caused by occupational exposure to asbestos, but secondary exposure is also a risk.

Mesothelioma

More research has been done on mesothelioma than any other asbestos-related cancer. As of 2011, more than 175 clinical trials have been conducted. Although first confirmed to have a causal relationship with asbestos in the United States in 1964, mesothelioma has demonstrated a correlation with asbestos since the 1920s. The cancer is almost exclusively caused by asbestos and is most often affiliated with heavy, short term exposure.

The two most common types of mesothelioma are pleural mesothelioma and peritoneal mesothelioma. Cases of pericardial and testicular mesothelioma have also been reported, both making up around 1 percent of mesothelioma patients. In the United States, between 2,000 and 3,000 mesothelioma cases are documented each year.

Lung Cancer

Lung cancer is a disease marked by abnormal cell growth in lung tissue. Although pleural mesothelioma receives more attention in the field of asbestos-related conditions, lung cancer is the most common asbestos-related cancer. The cancer is primarily associated with cigarette smoking, but approximately 10 percent of patients have no smoking history. By itself, asbestos exposure can cause lung cancer without any cigarette smoking. In these cases, the duration of exposure is generally more than five years.

The first possible connection between asbestos and lung cancer was reported in 1935. In 1942, the Director of Occupational Cancer Studies at the National Cancer Institute officially declared that asbestos was capable of causing lung cancer. The International Agency for Research on Cancer (IARC) reconfirmed in March 2009 that all commercial asbestos fibers cause lung cancer.

The likelihood of developing lung cancer after experiencing exposure is stronger for those who also smoke cigarettes. Research has indicated that the combination of smoking and asbestos exposure has a synergistic effect that results in a 50-fold increase for lung cancer risk. One explanation for this is that smoking may enhance the retention of asbestos fibers in the lung. According to researchers, when the carcinogens of cigarette smoke adhere to the surface of asbestos fibers, the chances of those fibers remaining embedded are much higher.

Ovarian Cancer

Ovarian cancer is the formation of cancerous growth that arises from the ovary. The first suggestion that asbestos could be associated with ovarian cancer was made in 1960 after reports indicated an increased amount of women with asbestosis developed the cancer. By 1967, clinical observations were made that detected a possible association between asbestos and ovarian cancer. Finally in 2009, the IARC confirmed that sufficient evidence exists to state that asbestos exposure causes ovarian cancer.

While some reports have shown a correlation between ovarian cancer and women occupationally exposed to asbestos, the use of asbestos-containing talcum powder on the genital area is most often studied when evaluating a causal relationship. Even women who do not use talc but have partners who do are at a 50 percent higher risk of developing ovarian cancer. Some studies suggest that ovarian cancer risk factors like asbestos in talc are more prevalent for persons with an increased genetic susceptibility to asbestos.

Laryngeal Cancer

Laryngeal cancer involves abnormal growth in the throat, and is most often caused by smoking cigarettes. However in 2006, the U.S. Institute of Medicine Committee on Asbestos concluded that there is sufficient evidence to support a causal relationship between asbestos exposure and laryngeal cancer. As recently as 2009, the IARC reconfirmed that asbestos can cause laryngeal cancer.

One of the primary reasons why laryngeal cancer has a causal relationship with asbestos is because the larynx lies directly in the path of a person's inhalation air stream. The most common method of asbestos exposure is inhaling airborne asbestos fibers. As asbestos fibers are repeatedly inhaled, the chance of the fibers hitting the larynx and becoming embedded increases. Although very rare, people previously exposed to asbestos may be at risk for developing laryngeal cancer.

Cancers Associated with Asbestos

A couple of cancers have an association with asbestos, but a causal relationship has not been determined. The cancers that fall under this category include gastrointestinal cancer and colorectal cancer. Although studies suggest there may be a causal relationship between asbestos and these cancers, more research is needed for confirmation.

Gastrointestinal Cancer

Gastrointestinal cancer can involve a number of regions in the body along the gastrointestinal tract, including the esophagus, stomach, liver, pancreas and bowels. Many organizations have determined there is an association between gastrointestinal cancer and asbestos. The World Health Organization concluded that there is a correlation between gastrointestinal cancers in people who work in occupations with a history of asbestos exposure. In addition, the Surgeon General of the United States and the Department of Health, Education and Welfare said that past asbestos exposure can result in an excess of gastrointestinal cancers.

Colorectal Cancer

Colorectal cancer is the development of abnormal cell growth in the colon, rectum or appendix. In 1986, the Occupational Safety and Health Administration included colorectal cancer in its list of cancers that needed to be evaluated by physicians during asbestos surveillance physical examinations. A number of studies have suggested an elevated risk of colorectal cancer in people exposed to asbestos, but this association is not yet confirmed.

Increased Risk Cancers

According to the National Toxicology Program, the National Cancer Institute and numerous other authorities, scientific studies have reported an increased risk for cancers of the esophagus, throat, gallbladder and kidney among those occupationally exposed to asbestos. No direct causal relationship has been proven for these cancers, but some data suggests these cancers occur more often in people who work around asbestos.

Studies on Other Cancers

Some other cancers have been studied for a potential connection to asbestos exposure. Although breast and prostate cancers are not considered asbestos-related diseases, they have been reported in excess among some scientific studies on asbestos exposure.

Breast and Prostate Cancer

Breast and prostate cancer have also been associated with asbestos exposure, but clear causal relationships for these cancers have not been established. For both breast cancer and prostate cancer, the few published studies do not show enough statistical significance to state that there is an association with asbestos, but some have reported an increased incidence. Several researchers have noted correlations between these cancers and asbestos, but more research is needed.

Even though some cancers have a firm connection and others do not, more research is needed so that anyone affected by an asbestos-related disease can receive proper treatment. For those who have been diagnosed with an asbestos-connected condition, working with mesothelioma or asbestos disease specialist can offer the best treatment for each individual case. If you'd like to be paired with a specialist or discover treatment facilities in your area, call (800) 381-1772 to learn more about available patient resources.

Sources

1. Dodson, R. and Hammar, S. (2011). Asbestos: Risk Assessment, Epidemiology, and Health Effects, Second Edition. Boca Raton: Taylor & Francis.
2. Gutman, H. (2005). Lung Cancer and Mesothelioma. United States: Xlibris.
3. Asbestos Exposure and Cancer Risk – National Cancer Institute. (2009) Retrieved from http://www.cancer.gov/cancertopics/factsheet/Risk/asbestos#r3
4. Report on Carcinogens, 12th Edition – National Toxicology Program. (2011) Retrieved from http://ntp.niehs.nih.gov/ntp/roc/twelfth/roc12.pdf
5. Laryngeal Cancer and Asbestos – Institute of Medicine (US) Committee on Asbestos: Selected Health Effects. (2006) Retrieved from http://www.ncbi.nlm.nih.gov/books/NBK20323/