Asbestos Cancer

Asbestos cancer is a malignant tumor caused by exposure to asbestos fibers. Asbestos exposure is most commonly associated with mesothelioma and lung cancer. Mesothelioma is a rare cancer affecting the lining of the lungs, heart, and abdomen, while traditional lung cancer occurs in the tissue of the lung’s lobes..

Pleural Mesothelioma and Asbestos

Pleural mesothelioma, the most common variety, is caused by inhaled asbestos fibers which lodge themselves in the pleural lining of the lungs. Asbestos fibers, which are microscopic but durable, then irritate the inner tissue, causing the growth of harmful scar tissue and eventually mesothelioma.

Peritoneal Mesothelioma and Asbestos

Peritoneal mesothelioma is less common and doctors have not exacted relationship between the asbestos exposure and the malignancy. However, nearly all peritoneal mesothelioma patients have a history of asbestos exposure. Peritoneal mesothelioma occurs in the lining of the abdominal cavity, near the digestive tract. Doctors surmise that ingested asbestos fibers lodge in the outer tissue of the organs and cause a similar inflammation as in the pleura.

Pericardial Mesothelioma and Asbestos

Pericardial mesothelioma occurs in the lining of the heart and is extremely rare. Like peritoneal mesothelioma, very little is known about the relationship between the malignancy and asbestos exposure but nearly all patients have asbestos exposure history. Physicians surmise that because the cancer occurs in the heart’s lining, the asbestos fibers may impact the heart through the bloodstream.

Lung Cancer and Asbestos

Asbestos has also been linked to cancers of the lung, as opposed to the pleural lining of the lungs. These are likely the result of malfunction caused due the exposure and inhalation of asbestos fibers, which can also cause chronic respiratory conditions such as asbestosis.

What is Asbestos?

Asbestos Fiber - For most individuals, especially those born in the last 40 years, the mention of asbestos conjures up thoughts of a dangerous substance that's sickened many people and caused myriad deaths around the world. That's an accurate description.

A common misconception on the part of many individuals, however, is that asbestos is a hazardous man-made substance, conjured up in factories around the world for commercial use. The truth is, however, that asbestos is a naturally-occurring mineral that can be found in hundreds of countries on just about every continent. As a matter of fact, asbestos is still mined in several of these countries, including Canada and Russia. Other countries have outlawed the mining of asbestos.

Asbestos is a highly-fibrous mineral with long, thin, separable fibers. The thin fibers can be spun and woven together, and possess valuable heat-resistant properties that make asbestos suitable for insulation and other such products. Indeed, for decades, asbestos was the material of choice for many industries that were manufacturing products for which heat resistance, low electrical conductivity, flexibility, and high tensile strength were essential factors. Today, there are other alternatives.

There are two kinds of asbestos. The serpentine variety is curly. Chrysotile asbestos, most commonly used for industrial purposes, is from the serpentine family. Other asbestos fibers, from the amphibole family, are very straight and needle-like. Amosite, crocidolite, tremolite, actinolite, and anthophyllite are amphibole asbestos varieties.

Currently, chrysotile asbestos is the only type mined on a wide-scale though a handful of countries continue to mine other forms. However, worldwide outrage about the use of dangerous asbestos has forced many countries to reconsider their position on mining.

Why is Asbestos a Health Concern?

Studies estimate that approximately 3,000 different types of commercial products include asbestos. In and of itself, the mineral is not harmful, as long as it's intact. However, when the asbestos in these products is damaged and the fibers become airborne, concerns begin to arise.

"Friable" asbestos - that which is dry and can be easily crumbled with the hand - is the culprit. Such asbestos is more likely to release fibers into the air. Spray-applied asbestos fireproofing, which was used in millions of buildings throughout the world, is of the friable variety. However, some non-friable asbestos can also release airborne fibers, particularly when sanded, chopped, hammered, cut, or otherwise manipulated. That's why, when demolishing a building that contains asbestos, proper removal and disposal in a designated asbestos landfill is essential before the building is torn down.

Why are Airborne Fibers Dangerous?

Inhaled asbestos fibers remain in the body and cannot be expelled. Because of this, the fibers can easily penetrate body tissues and may deposit themselves in airways and in the lung tissue. The more you're exposed, the more likely you might develop an asbestos-related disease. Most people exposed to asbestos on a very casual basis probably will not develop such a disease.

Once the fibers are lodged in the body, they will cause inflammation which may eventually result in the formation of cancerous tumors, particularly on the mesothelium - the lining of the lungs. Other affected areas may include the peritoneum - the lining of the abdomen - and the pericardium - the lining around the heart. There are various type of mesothelioma treatment options for each type.

With some recent exceptions found in workers at the World Trade Center disaster, asbestos-related diseases, such as pleural mesothelioma, usually surface several decades after exposure. That's why current cases of mesothelioma and other asbestos-related diseases involve many individuals who were employed in shipyards during World War II, performing jobs that exposed them to friable asbestos on a daily basis. Shipyard workers are among those most affected by aggressive asbestos cancer.

Is Asbestos Banned?

Contrary to what many people believe, asbestos is not and has never been banned in the United States. In 1976, Congress passed a law to regulate toxic substances (known as the Toxic Substances Control Act) but a total ban was not suggested. In 1989, the Environmental Protection Agency finalized regulations to ban asbestos under the aforementioned act, but two years later, a New Orleans circuit court of appeal overturned the regulation. The result was that new uses of the dangerous mineral were banned but old ones remained.

Many other industrialized nations have banned asbestos including the European Union and a handful of other countries, such as Chile, Croatia, Australia, Argentina, and Saudi Arabia. Several countries, especially those who continue to make money from the mining of asbestos, consistently fight against asbestos bans.

A few current U.S. senators, with the assistance of asbestos watchdog groups, hope to encourage the government to reconsider a ban on all asbestos products. A new bill, called the "Ban Asbestos in America Act of 2007" (S.742), was introduced by Senator Patty Murray on March 1, 2007.

Pericardial Mesothelioma

Pericardial mesothelioma is a very rare cancerous disease of the tissue layers surrounding the heart. The mesothelium membrane is comprised of two layers, one that adheres to a moving internal organ such as the heart or lungs, and the other which forms a sac around the organ. The tissues secrete a lubricant that allows the active organ to move easily against adjacent structures, such as the rib cage and diaphragm. The peritoneum is the mesothelial layer that lines the abdominal cavity, the pleura lines the chest cavity, and the pericardium surrounds the heart. Abnormal growth (cancer) in the cells of any of these mesothelial structures is referred to as mesothelioma.

The primary cause of mesothelioma is exposure to asbestos in the workplace, even for brief periods, with symptoms sometimes taking up to 50 years after exposure to become apparent. Among the populations most effected by mesothelioma are miners who were employed in South Africa and Australia (including a large number of Italian immigrants), who often worked in dusty conditions without protective equipment. Among Americans and Europeans, most cases have arisen among those who worked with asbestos in the construction trades and shipbuilding, where asbestos was used extensively for its insulating properties and as a fire retardant. At this point, however, there is insufficient evidence to link pericardial mesothelioma to asbestos exposure. Similarly, smoking does not appear to be a risk factor for mesothelioma.

Pleural mesothelioma often spreads to the pericardium in its advanced stages. Primary pericardial mesothelioma (where the tumor starts in the pericardium) is rare, making up less than 1% of total mesothelioma cases. Histological types include epithelial, sarcomatous, and mixed.

In the history of medicine pericardial mesothelioma has also been called endothelioma, coelothelioma, and endothelial carcinoma. There are other types of pericardial tumors, but about half are mesothelioma. The others are usually sarcoma (angiosarcoma) and can be difficult to distinguish from sarcomatoid pericardical mesothelioma.

The disease occurs across all age groups, almost equally in both sexes. With the elimination of asbestos in many building products and an overall improvement in working conditions and health monitoring, it is likely that the overall incidence of mesothelioma will decline in the next decade or so. In the absence of the identification of a principle causative agent, it is less clear whether the incidence rate of primary pericardial mesothelioma will change.

Results from an extensive study of autopsy records from 500,000 people who had died from cancer showed that primary tumors of the pericardium were responsible in only 0.0022% of the cases. With respect to all pericardial and cardiac primary tumors, only 2 or 3 percent are associated with mesothelioma, well behind the numbers for angiosarcoma (33%) and rabdomyosarcoma (20%).

Symptoms

The symptoms are dyspnea and pain pleural effusion, inflammation of the pericardium (called pericarditis). A dangerous symptom is cardiac tamponade in which blood accumulates in the pericardium and can lower the heart’s pumping stroke volume. These symptoms are common to other forms of mesothelioma and to a number of other conditions affecting the heart and lungs, such as pneumonia and lung cancer. In many cases, symptoms are not apparent until the disease has progressed to advanced stages, leaving few options for effective treatment.

Diagnosis

While doctors can examine fluid from the pericardial cavity (similar to the examination of pleural effusion fluid in diagnosis of pleural mesothelioma), malignant cells are found only 30% of the time, which is another reason this cancer is so hard to diagnose. CT scans can sometimes reveal thickening of the pericardium and a tumor mass is visible, although less than half of the time. Diagnosis of pericardial mesothelioma often takes place when the disease is quite advanced, at a point when the tumor and associated swelling are constricting other thoracic structures such as veins, arteries and airways. Pericardial swelling can also be associated with tuberculosis, rheumatoid arthritis, and other conditions. There was even a recent Japanese report about a patient who appeared to have pericardial constriction, which later turned out to be mesothelioma. A British case report about a young man with pericardial mesothelioma that confounded doctors “illustrates the difficulty in establishing this diagnosis by echocardiography and computed tomography.”

Pericardial mesothelioma often can appear to be rheumatic fever, lupus erythematocous, and tuberculosis pericarditis.

Radiography and other imaging techniques (e.g., echocardiography and magnetic resonance angiography) can be used to demonstrate swelling of the pericardium. In some cases, the myocardium and coronary arteries might also be involved. Isotope scans with gallium or technetium as well as cardiac catheterization can be used to measure decreased function in the heart and blood vessels. Post-contrast computerized tomography can be used to differentiate the tumor mass from the rest of the swollen tissue surrounding the heart. However, even with the identification of a tumor, the use of imaging techniques alone will not result in a definitive diagnosis because melanoma, leukemia and lymphoma can also involve the pericardium. Precise diagnosis requires demonstrating that the tumor has no relationship with the pleural surfaces.

Standard laboratory tests of blood, urine, and sputum are of little help in detecting mesothelioma. Liquid extracted from the swollen area can provide adequate cytological evidence for accurate diagnosis, but in some cases this method has resulted in a misdiagnosis, indicating other cancers (e.g., adenocarcinoma).

A biopsy carried out on a tissue sample obtained by thoracoscopy or sternoscopy is the only way to substantiate a positive identification of mesothelioma. In terms of specific laboratory indicators for the presence of mesothelioma, the cancer cells stain positive for cytokeratin, vimentin, epithelial membrane antigen, and calretinin and negative for CEA, CD15, CD34 and S-100. In 60 to 80 percent of cases, accurate diagnosis based on histological analysis of tissue samples is only accomplished after the death of the patient.

Treatment

The choice of treatment regimen is dependent on how far the cancer has progressed at the time a positive diagnosis is made, and is also be based on the age, weight, medical history, and general well-being of the patient.

With early detection, when the tumor mass is small and localized, radical surgery for removal of cancerous tissue is possible but risky, given the proximity to the heart and lungs. If the cancer has spread to the lymph nodes, lungs, chest wall, or other organs (as it does in 25 to 45 percent of cases), surgical removal is no longer an option.

A course of palliative surgery for draining fluid from the pericardium, as a means of relieving pressure on proximal structures, can be used to alleviate symptoms and as a way to obtain a tissue sample for biopsy. This procedure can be used to help prolong life while other treatment modalities are administered.

Radiation therapy can be used to kill the cancer cells and shrink tumors, but this approach carries with it the risk of damaging the heart and lungs. As well as the more familiar practice of external exposure to radioactive materials, treatment might involve delivering radioactive materials directly to the cancer site through plastic tubing (internal therapy).

No chemotherapeutic agents have been shown to be effective in the treatment of pericardial mesothelioma. There was a recent case report from India about success in one patient using a combination of pemetrexed and cisplatin, the same regimen used in treatment of pleural mesothelioma.

Prognosis

Although there are few cases of primary pericardial mesothelioma, it appears that the prognosis for this cancer is worse than it is for pleural or peritoneal mesothelioma. As a direct consequence of the difficulties in definitively diagnosing pericardial mesothelioma and the fact that it usually only minimally symptomatic until its advanced stages, the prognosis for patients is very poor, with a mean survival time of only six months following diagnosis. Death often occurs as the result of congestive heart failure or occlusion of the superior vena cava. This situation is unlikely to change without significant advances in early detection techniques and treatment regimens.