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Malignant Mesothelioma

Definition

Malignant mesothelioma is a type of cancer that can develop in the linings of the chest or abdomen.

What is going on in the body?

Mesothelioma is an aggressive cancer that is almost always linked with exposure to asbestos and smoking tobacco. It is frequently found in the lining that surrounds the lungs, called the pleura.
Mesothelioma can also affect:
  • the chest wall
  • the inside of a person's chest, or thorax
  • the muscle that separates the chest and stomach cavities, which is called the diaphragm
  • the peritoneum, the membrane that lines the abdominal cavity
There may be one or more tumors, which can grow to a large size and may invade neighboring tissues. These tissues can include the chest wall, heart surface, diaphragm, liver, abdominal and pelvic organs, or blood vessels and nerves. The tumor can also spread through the blood to other organs such as the liver.

Risks

What are the causes and risks of the disease?

Asbestos exposure is the primary risk factor for mesothelioma. People who have mined, milled, or worked with asbestos are at high risk for this disease. Laborers who work with plumbing, boilers, or other heating equipment that uses asbestos are also at risk. Others who do not work directly with asbestos but are in the area where the substance is being used are also at risk. This may include carpenters, electricians, or welders.
People who live with asbestos workers, such as spouses and children, also have a higher risk of mesothelioma. It takes 30 to 40 years from the time of asbestos exposure for mesothelioma to develop. This cancer is diagnosed in roughly two to three thousand people in the U.S. each year. The rate has declined since the mid-1990s, reflecting the fact that the asbestos industry has been regulated for many years.
Since the primary means of exposure has been due to working with asbestos, the rate of this cancer is three to five times higher in men than in women. The disease is extremely rare in children. Mesothelioma also has been linked to exposure to silicate-type minerals in other parts of the world. Cigarette smoking further increases the risk of mesothelioma in those exposed to asbestos.

Prevention

What can be done to prevent the disease?

Since the 1970s, the Environmental Protection Agency (EPA) and the Occupational Safety and Health Administration (OSHA) have regulated the asbestos industry in the U.S. In the past, asbestos was used as a fire retardant and an insulator. Other products are now used in its place.
The controversy involving exposure to different forms of asbestos continues. There are two major types of asbestos called chrysotile and amphibole. It is thought that the amphibole form of asbestos is to blame for causing mesothelioma.
However, asbestos is still being removed even if it is the chrysotile variety. Removal is taking place in schools and other public buildings throughout the U.S. The hope is that these measures will greatly reduce the occurrence of this cancer.
Stopping smoking will also reduce the risk of mesothelioma in those who have been exposed to asbestos.

Diagnosed

How is the disease diagnosed?

Diagnosis of mesothelioma begins with a medical history and physical exam. The healthcare professional may order a chest X-ray and a chest CT scan or chest MRI.
The diagnosis is confirmed with a biopsy. A tissue sample can be obtained through a needle, called a needle biopsy. Alternatively, an incision known as a thoracotomy can be made in the chest in order to remove the tumor. The area in question can also be viewed with a scope, known as a thoracoscope or peritoneoscope.
Staging of mesothelioma that affects the pleura can be important in deciding on treatment.
  • Stage I means that the cancer affects the outer edges of pleura on only one side of the body.
  • Stage II means that the cancer has invaded the pleura and may have spread to the esophagus or heart.
  • Stage III means the cancer has spread to the membrane lining the abdominal cavity, called the peritoneum.
  • Stage IV means the cancer has spread throughout the body via the bloodstream.
Mesotheliomas that affect the peritoneum often occur in more than one place; however, the numbered staging system does not apply to these tumors. The cancer is usually confined to the abdomen and can often be seen on an abdominal CT scan or abdominal MRI. There is no specific laboratory test for mesothelioma other than examination of the tumor tissue itself.

Long Term Effects

What are the long-term effects of the disease?

A mesothelioma is a highly aggressive tumor that is most often fatal. Current treatment of malignant mesothelioma is designed to make the person with cancer comfortable. Long-term survival cannot usually be expected. .

Other Risks

What are the risks to others?

Mesothelioma is not contagious and cannot be passed from one person to another. The exposure to the asbestos that caused the cancer occurred many years to several decades before the disease appeared. People who live with asbestos workers have a higher risk of getting this cancer.

Treatments

What are the treatments for the disease?

Surgery may be able to cure the disease in Stage I and, in some cases, in Stage II. Before performing surgery, the healthcare professional must determine if the tumors are operable. The person must also have adequate heart and lung function. Surgery can involve removal of the pleura and pleural-based tumor. Some people may need to have the lung on that side of the body removed as well.
Individuals with peritoneal mesothelioma can sometimes benefit from surgery. Operations can remove fluid buildup, bowel obstruction, or other problems. They may also relieve pain linked with these conditions. If the cancer has invaded the chest wall, heart, lymph nodes, or diaphragm, surgery probably will not help. People in whom the cancer has spread to distant sites will also not be helped by surgery.
Different forms of radiation therapy can be used. These include:
  • colloidal radioactive chemicals placed into the pleural cavity or peritoneum
  • a combination of colloidal radioactive chemicals and radiation implants
  • radiation implants in the pleural cavity or peritoneum
  • radiation of the chest wall
Medicines used for chemotherapy include doxorubicin (i.e., Adriamycin), dacarbazine (i.e., DTIC-Dome), mitomycin (i.e., Mutamycin), and cisplatin (i.e., Platinol_. The therapy is primarily to ease discomfort. This type of chemotherapy can be combined with radiation. It can also be given directly into the pleural or peritoneal space.

In its advanced stage, this cancer is not considered curable. In this case, treatment involves making the person comfortable. Efforts to ease symptoms may include:

  • intravenous glucose
  • narcotic pain medicine
  • removal of pleural or peritoneal fluid

Side Effects

What are the side effects of the treatments?

Because of the extensive nature of the operation needed, the person sometimes does not survive the surgery. Other possible side effects of the surgery include:
  • accumulation of pus, called empyema
  • reactions to anesthesia
  • bronchopleural fistulas, which are abnormal openings between the airways and the lining of the lungs
  • chronic lung failure
  • infection
  • loss of lung function
  • serious bleeding during surgery with need for blood replacement
  • vocal cord paralysis
Radiation frequently damages the lung. Significant injury to other normal tissues including the heart and liver is possible.
Single-agent or multiple-drug chemotherapy can be toxic. Use of combination agents is likely to cause:
  • bone marrow suppression, in which the bone marrow is not able to produce normal types and amounts of blood cells
  • diarrhea
  • hair loss
  • increased risk of infection
  • mouth sores

After Treatment

What happens after treatment for the disease?

After treatment, the individual will be monitored for lung, heart, and other organ function. Some people who have had a lung removed may need to continue using oxygen.

Monitor

How is the disease monitored?

Monitoring includes physical exams, blood tests, chest X-rays, and CT scans. There is no specific blood test that accurately predicts recurrence. Mesothelioma can come back several months to a few years later. A second tumor, independent of the first, has been known to occur as well. Any new or worsening symptoms should be reported to the healthcare professional.

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