Mesothelioma

Mesothelioma Related Articles

What Is Mesothelioma?

Mesothelial cells are a layer of specialized cells that line the body cavities, including the pleura (lining of the lung), peritoneum (lining of the abdominal cavity), and pericardium (lining of the heart). The tissue formed by these cells is called mesothelium.

The mesothelium contains both an outer and an inner layer. The inner layer surrounds the organs themselves, while the outer layer lines the body cavities in which the organs covered by mesothelial cells reside. The mesothelial cells themselves produce and secrete a small amount of lubricating fluid between the two layers that permits the organs to move smoothly against adjacent organs and structures.

Like other cells of the body, mesothelial cells can also grow abnormally, leading to the development of tumors. The tumors of the mesothelial cells can be benign (noncancerous) or malignant (cancerous). A malignant tumor of the mesothelium is called a malignant mesothelioma. Because most mesothelial tumors are cancerous, malignant mesothelioma is often simply referred to as mesothelioma. This article focuses on mesothelioma of the lining of the lungs (pleural mesothelioma), which is the most common form of all mesotheliomas.

Mesothelioma is an uncommon disease. The disease is more common in men of Caucasian and Hispanic ethnicity, and less common among Asian and African American men. The disease shows a male predominance, which is like due to occupational exposure.

The main risk factor for developing pleural mesothelioma is exposure to asbestos. Asbestos is a mineral that occurs naturally as strong, flexible fibers that can be separated into thin threads and woven. Asbestos has been widely used in many industrial products, including cement, brake linings, roof shingles, flooring products, textiles, and insulation. If tiny asbestos particles float in the air, especially during the manufacturing process, they may be inhaled or swallowed.

Prior to the 1970s, enormous amounts of asbestos were used in commercial construction and shipbuilding. After the health risks of asbestos became known, production of asbestos slowed drastically in the 1970s. Governmental restrictions were placed on its use, and alternative materials became available. Despite these changes, asbestos continues to be used.

Occupations that deal with asbestos and typically associated with the onset of mesothelioma later in life include asbestos production, insulation work, heating trades, shipyard work, and construction.

The period between asbestos exposure and the development of mesothelioma is generally 35-40 years. Usually, people who develop mesothelioma have been exposed to asbestos for a prolonged period of time; however, some people with only brief exposures have also developed mesothelioma. On the other hand, not all workers who are heavily exposed develop mesothelioma.

Mesothelioma can also occur in family members and other people living with asbestos workers. It may be a result of exposure to asbestos dust brought home on the clothing and hair of asbestos workers.

In some people with mesothelioma, no specific asbestos exposure can be found. Frequently, such people have worked in a job where the exposure was not recognized or typically associated with asbestos exposure. Mesothelioma without asbestos exposure does occur.

What Causes of Mesothelioma?

Asbestos

The major known cause of mesothelioma is exposure to asbestos. A known history of asbestos exposure is present in a majority of cases of mesothelioma. Asbestos likely causes cancer by physically irritating the cells. When asbestos fibers are breathed in, they reach the ends of the small airways and penetrate into the pleura (lining of the lung). These fibers may then injure mesothelial cells of the pleura and eventually cause mesothelioma.

The risk of developing mesothelioma rises with the quantity of asbestos exposure. However, genetic factors also play a role in determining who develops the condition. This is probably the reason why all people exposed to high levels of asbestos do not develop mesothelioma.

Smoking

Although smoking has not been associated with the development of mesothelioma, the combination of smoking and asbestos exposure significantly increases a person's risk of developing lung cancer.

Other Causes

Mesothelioma also has been linked to the following:

  • Radiation: Mesothelioma has been reported to occur in few people following exposure to therapeutic radiation using thorium dioxide (Thorotrast).
  • Zeolite: Zeolite is a silicate mineral (chemically related to asbestos) commonly found in the soil of the Anatoli region of Turkey. A few cases of mesothelioma reported from this region may have been caused by zeolite.
  • Simian virus 40 (SV40): The role of SV40 in the development of mesothelioma has also been suggested. This virus has been identified in human mesothelioma cells. In studies conducted in animals, it has been shown to induce the development of mesothelioma. In humans, the possibility of SV40 serving as a cofactor in the development of mesothelioma is inconclusive and further research is ongoing.

What Are Mesothelioma Symptoms and Signs?

Symptoms of mesothelioma may not appear until 30 to 50 years after exposure to asbestos. The onset of symptoms is gradual, and a person often experiences symptoms for four to six months before the diagnosis is made.

You should see a health-care provider if you have any of the following symptoms:

The above listed symptoms may be caused by mesothelioma or by other, less serious diseases. Only a health-care provider can make a diagnosis with the help of various exams and tests.

What Specialists Treat Mesothelioma?

Patients with mesothelioma will usually require treatment by an oncologist (cancer specialist) or pulmonologist (lung specialist).

How Do Specialists Diagnose Mesothelioma?

Imaging Studies

Chest X-ray: In people with mesothelioma, chest X-ray may show signs of mesothelioma. However, chest X-ray has limited usefulness because the findings of mesothelioma on chest X-ray are nonspecific and observed in other diseases as well.

CT scan: The findings of CT scan are similar to those of chest X-ray but are seen better and in more detail. CT is preferred for staging (evaluating the extent of) the tumor.

MRI: In some people, MRI complements the findings on CT scan. MRI provides better demonstration of soft tissues (better soft-tissue contrast) and may provide additional information not obtained from other studies.

Positron emission tomography (PET) scan: PET is a procedure in which a radiolabeled substance is used to measure the metabolic activity of the cells. Cancerous cells demonstrate increased metabolic activity. This procedure is being increasingly used to determine the size of the tumor and whether the tumor has spread.

Radiologic findings on X-ray, CT scan, and MRI cannot provide a clear diagnosis of mesothelioma. A history of asbestos exposure and radiologic findings may indicate the presence of mesothelioma, but it is important to stress that a diagnosis of mesothelioma cannot be made exclusively with imaging. Other diseases can look identical to mesothelioma radiographically. Tissue biopsy (a sample of cells is removed for examination under a microscope) is required for a definitive diagnosis.

Thoracoscopy: In this procedure, a small cut is made in the chest wall and a thoracoscope (flexible, lighted tube) is inserted between the two ribs. Thoracoscopy allows the health-care professional to look inside the chest and take tissue samples. A pathologist examines these samples for cancer cells. It provides a confirmatory diagnosis in 98% of people with mesothelioma.

How Do Doctors Determine Mesothelioma Staging?

When the diagnosis of mesothelioma is confirmed, the tumor stage is determined in order to plan the optimal treatment. Mesothelioma is broadly staged into two categories: localized (the tumor is restricted to the membrane surface where it originated) and advanced (spread to neighboring structures and distant organs and tissues).

Localized mesothelioma is also called stage I mesothelioma.

Advanced mesothelioma can be further classified into the following stages:

  • Stage II: The tumor has spread beyond the lining of the chest wall to lymph nodes in the chest.
  • Stage III: The tumor has spread into the chest wall, mediastinum (area of the chest between the lungs), heart, diaphragm (thin muscle below the lungs and heart that separates the chest from the abdomen and helps in breathing), or abdominal lining.
  • Stage IV: The tumor has spread to distant organs or tissues.

What Are Treatments for Mesothelioma?

Like most cancers, mesothelioma is best treated when it is diagnosed early. Treatment depends on the location of the tumor, how far it has spread, and your age and general health. Stages 1, 2, and some stage-3 mesothelioma may be amenable to potentially curative surgery. Whatever the stage of mesothelioma, there are several types of treatments that can be used.

Traditional treatments for mesothelioma include the following:

  • Surgery (removal of the tumor)
  • Chemotherapy (using medications to kill cancer cells)
  • Radiation therapy (using high-dose X-rays or other high-energy rays to kill cancer cells)

Currently guidelines such as those provided by the National Comprehensive Cancer Network (NCCN) can guide treatment once the disease is diagnosed with certainty. Treatment is best done at centers with experience with this uncommon disease. Often the traditional treatments are used in combination. Aggressive surgery may carry significant risk of complications and is again best performed by experienced surgeons. A multidisciplinary team is usually convened prior to treatment to plan and coordinate the care of a patient with mesothelioma.

Because mesothelioma is difficult to treat, several new therapies are being evaluated currently. They include the following:

  • Photodynamic therapy
  • Immunotherapy
  • Gene therapy
  • Clinical Trials of new medications are ongoing

What Is the Medical Treatment for Mesothelioma?

Chemotherapy

Chemotherapy uses anticancer drugs to attempt to destroy cancer cells. Chemotherapy is a systemic treatment because the drug enters the bloodstream, circulates throughout the body, and kills cancer cells. Because the drugs circulate throughout the body, they can kill normal cells together with the cancer cells, leading to side effects. Chemotherapy is often used in combination with other treatments, especially surgery. Today the combination of two drugs, Pemetrexed and cisplatin has shown the most promise as a treatment.

Radiation Therapy

Radiation therapy is the use of high-energy X-rays or other high-energy rays to destroy cancer cells. Most of the normal cells recover from the injury caused by radiation; however, damage to some of the healthy cells causes the side effects of radiation therapy (nausea, vomiting, fatigue, hair loss, and skin irritation).

Radiation can be given from outside the body using a machine (external radiation therapy), or it can be given with the help of materials producing radiation that are implanted inside the body (internal radiation therapy).

Thoracentesis

To relieve symptoms and provide pain relief, your fluid from the pleural cavity may be drained by inserting a needle into the chest and applying gentle suction. Drugs may be given through a tube in the chest to prevent more fluid from accumulating.

Surgery for Mesothelioma

The objective of surgery is to remove the mesothelioma. If the tumor has spread to many organs, it is impossible to remove all the cancer cells from the body. In such cases, surgery may still be done to provide pain relief.

Depending on the stage of the tumor, the surgeon may decide on the type of surgery. Types of surgeries for pleural mesothelioma include pleurectomy and extrapleural pneumonectomy.

  • Pleurectomy: In this type of surgery, the surgeon strips off both the layers of the affected mesothelial lining surrounding the lung. It is not a curative surgery because complete removal of all the mesothelial lining is not possible; therefore, the tumor recurrence rate is high. However, this procedure provides pain relief.
  • Extrapleural pneumonectomy: This is a very extensive surgery in which not only the affected pleural lining is surgically removed but that side of the lung, diaphragm, and mesothelial lining of the heart are also removed. This type of surgery is used when the tumor has not spread to the mediastinal lymph nodes.

Clinical Trials for Mesothelioma

Because mesothelioma is difficult to treat, clinical trials are being conducted to find new and better methods of treatment. Research is being conducted at various cancer centers all over the United States. Before any new treatment can be used at large, specialists conduct trials in a limited number of people to ascertain whether the treatment is useful and safe. If you have mesothelioma, you have an option of enrolling in the various clinical trials being conducted.

If you are considering enrolling yourself in a clinical trial, you may find the booklet Taking Part in Clinical Trials: What Cancer Patients Need to Know useful. This booklet published by the National Cancer Institute explains how research studies are done and describes their possible benefits and risks. You can order the booklet by calling Cancer Information Service at 1-800-4-CANCER (1-800-422-6237); TTY at 1-800-332-8615.

Web sites giving information about ongoing clinical trials include the following:

Palliative Care for Mesothelioma

In some people, age, other health problems, or advanced disease may make aggressive treatment of mesothelioma difficult. In such people, palliative care (treats the symptoms, but not the disease itself) is an option. Palliative care is a specialized form of care that lessens pain and other symptoms. The goal of palliative care is not to prolong life or hasten death, but rather to enhance the quality of your life, while offering support to you and your family. Your doctor should offer you palliative care consultation as part of your treatment planning especially in inoperable mesothelioma or in cases where you are not well enough to undergo such surgery.

If you opt for palliative care, it is very important to communicate openly with your health-care provider. With palliative care, many symptoms of mesothelioma can be substantially reduced. At every visit, you should tell your health-care provider how you feel, what discomfort you have, and your level of pain.

Palliative care offers you emotional and physical comfort and relief from pain. Other symptoms managed through palliative care include shortness of breath, fatigue, loss of appetite, gastrointestinal problems, skin problems, anxiety, and depression.

Palliative and, eventually, end-of-life care may be given in a hospital, hospice, or nursing home; however, it can also be provided at home. The following organization can help you with palliative and terminal care:

National Hospice and Palliative Care Organization (NHPCO)
http://www.nhpco.org

Hospice Association of America (HAA)
http://www.nahc.org/

Hospice Education Institute
http://www.hospiceworld.org

Hospice Net
http://www.hospicenet.org

What Is the Prognosis of Mesothelioma?

Like most cancers, the outlook of mesothelioma depends on how early it is diagnosed and how aggressively it is treated. Without treatment, mesothelioma is fatal within four to eight months.

With trimodal treatment (surgery, chemotherapy, and radiotherapy), survival was noted in some people at 16-19 months. A few people survived as long as five years.

Is It Possible to Prevent Mesothelioma?

Because asbestos is the major known cause of mesothelioma, eliminating the exposure to asbestos can significantly decrease the risk of mesothelioma.

If you are exposed to asbestos at the workplace, you should wear protective clothing and masks. You should change your clothing before leaving the workplace to avoid carrying any asbestos particles home. Occupational Safety and Health Administration (OSHA) provides useful safety and health information for people exposed to asbestos.

Mesothelioma Support Groups and Counseling

Dealing with a life-threatening disease is difficult. Reading the experiences of other people with mesothelioma helps to cope with the condition. You can access their stories at the following Web pages:

Cough is a common symptom of mesothelioma.

Mesothelioma Symptom

Cough

Any environmental substance that irritates the air passages or the lungs is capable of producing a chronic cough with continued exposure. Cigarette smoke is the most common cause of chronic cough. Other cough-producing irritants include dusts, pollens, pet dander, particulate matter, industrial chemicals and pollution, cigar and pipe smoke, and low environmental humidity.

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Reviewed on 11/20/2017
Sources: References

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