Asbestos Cancer Overview

The major health risks associated with asbestos are due to its tendency to separate into microscopic particles that can become airborne and that are then easily inhaled or swallowed. Exposure to asbestos can lead to several types of life-threatening diseases, including asbestosis, lung cancer and mesothelioma, which is a cancer of the lining of the chest, abdomen, or heart. These three diseases are the most frequent causes of death among people with heavy asbestos exposure.

It is estimated that between 1940 and 1979, over 27 million people were exposed to asbestos in the course of doing their jobs in the United States. People who work with asbestos are not the only ones at risk. Before occupational safety regulations regarding asbestos were put into place, workers often brought home asbestos on their clothing, exposing their family members to the fibers as well. Also, people who live or work near asbestos-related operations can be exposed to asbestos that is released into the environment.

The chances of developing asbestos-induced lung cancer or mesothelioma increase in relation to how much asbestos a person is exposed to and how long the exposure lasts. However, researchers have found asbestos-related diseases in individuals with only brief exposures.

Mesothelioma

While relatively rare, with between 2000 and 3000 new cases reported in the U.S. each year, mesothelioma is still a significant risk to people exposed to asbestos. Because mesothelioma symptoms are similar to those of other diseases, and because the disease can take 40 years or more to manifest after asbestos exposure, there is some concern about misdiagnosed mesothelioma cases and questions as to whether the disease is underreported. However, it is agreed that asbestos exposure is the primary cause; in almost all cases, patients who are diagnosed with mesothelioma have been exposed to asbestos in the past.

More men are diagnosed with mesothelioma than women, although the gap between men and women is closing. The rate of female patients with mesothelioma has remained relatively steady while men's rates have dropped. It is thought that this discrepancy is due to fewer men being exposed to asbestos at work since health and safety regulations have been enacted in what have often been male-dominated occupations such as construction, railroad work, and shipbuilding. Like other cancers, the risk of developing mesothelioma increases with age.

When asbestos fibers are inhaled or swallowed, they can work their way to mesothelium tissues, which are the linings that surround organs in the body cavity. Pleural mesothelioma is a cancer of the pleura, the covering around the lung. While pleural mesothelioma is the most common form, peritoneal mesothelioma (cancer of the lining of the abdomen) can also be the result of asbestos exposure. In addition to pleural and peritoneal mesothelioma, cancer can develop in the lining around the heart. This cancer, called pericardial mesothelioma, is the least common of the mesotheliomas.

Ninety percent of all pleural mesothelioma patients experience shortness of breath or some sort of chest pains. Over 80% develop pleural effusions, or an increase of fluids between the linings of the lungs and the linings of the chest. In some cases, pleural effusions do not cause discomfort and are only found when the chest is x-rayed. Other symptoms may include unexpected weight loss, loss of appetite, fever, or the coughing of blood.

The symptoms of peritoneal mesothelioma can include losing weight even while experiencing an increase in the size of the waist. Some patients retain fluids or develop tumors in their abdomens, leading to swelling or pain in that area. Other symptoms may include anemia, fever, and blockages in the intestines.

Diagnosis generally starts with an X-ray, MRI, or CAT scan of the abdomen or chest. Additional tests might include a thoracoscopy, a procedure that involves cutting between two ribs and inserting a thoroscope into the chest, or a peritoneoscopy, where a peritoneoscope is inserted through an incision into the abdomen.

Surgery is the most frequently used method of treating mesothelioma. The location and size of the cancerous tumor determines the type of surgery required. A surgeon may have to remove some of the abdominal lining, part of the chest, or part of a lung. Radiation, both external and internal, and chemotherapy are other therapies that are used to fight mesothelioma.

Several new types of treatments for mesothelioma are also being studied. Intraoperative photodynamic therapy involves injecting a drug that makes the cancer sensitive to light a few days before surgery. During surgery, a special type of light is shined on the cancerous area in addition to removing as much of the tumor as possible. In addition, both immunotherapy, which is a treatment that involves using the patient's own immune system to fight mesothelioma, and gene therapy to change the genes involved in growing cancerous tumors are in clinical test stages.

Unfortunately, mesothelioma cannot be cured with today's medical knowledge, and the average survival time after diagnosis is only one year. About 10% of people diagnosed with mesothelioma survive for more than five years.

Asbestos-Induced Lung Cancer

The average man in the U.S. has a one in 12 chance of getting lung cancer and the average woman a one in 16 chance. Asbestos workers, however, are about seven times more likely to die of lung cancer than people in general. Asbestos workers who smoke have a 50 to 90 times greater chance of getting lung cancer than the general population.

Most asbestos-induced lung cancer starts in the lining of the bronchi, which are the air tubes within the lungs. However, lung cancer can also begin in other areas of the pulmonary system. Although asbestos lung cancer usually develops slowly and may not appear until many years after exposure to asbestos, once it does occur, cancerous cells can metastasize, or spread to other parts of the body.

The two most common types of lung cancer are small cell lung cancer and non-small cell lung cancer. Asbestos exposure can be a factor in developing either type of lung cancer. Non-small cell lung cancer accounts for 85% to 90% of lung cancers.

People with early-stage asbestos-induced lung cancer often display no symptoms. In later stages, the most common symptoms include
a persistent cough; chest pain that is often worsened by deep breathing, coughing or even laughing; hoarseness; weight loss and loss of appetite; bloody or rust-colored sputum (spit or phlegm); difficulty breathing or shortness of breath; susceptibility to bronchitis and pneumonia; and wheezing.

The methods used to diagnose asbestos lung cancer include imaging tests such chest X-rays, CAT scans, MRIs and PET scans. If cancer is indicated, then tissue samples are used to confirm that it is cancer and to determine what type. These tests include biopsies, phlegm samples, and blood tests.

Non-small cell lung cancer can be treated with surgery, radiation therapy, chemotherapy, and targeted therapy (therapy that uses drugs designed specifically to target cancer cells and to interfere with their ability to grow). Surgery is the only method that is considered to be a reliable cure for non-small cell lung cancer. The rarer small cell lung cancer is usually treated with chemotherapy, sometimes together with radiation therapy; small cell lung cancer is very rarely treated with surgery.

The prognosis for neither type of lung cancer is good. Nearly 60% of those diagnosed with lung cancer die within one year, and nearly 75% die within two years. About 16% of people diagnosed with non-small cell lung cancer survive the disease for more than five years; only about six percent of those diagnosed with small cell lung cancer survive more than five years.

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