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Malignant pleural mesothelioma

Mesothelioma

Overview

Malignant mesothelioma is a form of cancer that develops in the thin layer of tissue that surrounds the lungs (pleura), chest wall, or abdomen. Signs and symptoms of the condition can vary and often depend on which area of the body is affected. Common features include abdominal bloating, abdominal pain, chest pain, coughing, fatigue, shortness of breath, and/or weight loss.

Malignant mesothelioma is thought to be caused by long-term exposure to asbestos (a fire-resistant material that was once commonly found in insulation; ceiling and roof vinyls; cement; and automotive brake materials). Most people appear to be diagnosed with the condition approximately 30 years after being in contact with the asbestos. Unfortunately, there is generally no cure for malignant mesothelioma unless it is diagnosed at an early stage and can be surgically removed. If surgery is not an option, chemotherapy and/or radiation therapy may still be recommended to help alleviate some of the associated symptoms.

Symptoms - Malignant pleural mesothelioma

Signs and symptoms of mesothelioma vary depending on where the cancer occurs. In the case of pleural mesothelioma, which affects the tissue that surrounds the lungs, causes signs and symptoms that may include:

  • Chest pain under the rib cage
  • Painful coughing
  • Shortness of breath
  • Unusual lumps of tissue under the skin on your chest
  • Unexplained weight loss

As pleural mesothelioma spreads in the chest, it puts pressure on the structures in that area. This can cause complications, such as:

  • Difficulty breathing
  • Chest pain
  • Difficulty swallowing
  • Pain caused by pressure on the nerves and spinal cord
  • Accumulation of fluid in the chest (pleural effusion), which can compress the lung nearby and make breathing difficult

Causes - Malignant pleural mesothelioma

In general, cancer begins when a series of genetic mutations occur within a cell, causing the cell to grow and multiply out of control. It isn't clear what causes the initial genetic mutations that lead to mesothelioma, though researchers have identified factors that may increase the risk. 

Asbestos exposure: The primary risk factor for mesothelioma:

Asbestos is a mineral that's found naturally in the environment. Asbestos fibers are strong and resistant to heat, making them useful in a wide variety of applications, such as in insulation, brakes, shingles, flooring and many other products.

When asbestos is broken up, such as during the mining process or when removing asbestos insulation, dust may be created. If the dust is inhaled or swallowed, the asbestos fibers will settle in the lungs or in the stomach, where they can cause irritation that may lead to mesothelioma. Exactly how this happens isn't understood. It can take 20 to 40 years or more for mesothelioma to develop after asbestos exposure.

Most people with years of asbestos exposure never develop mesothelioma. And yet, others with very brief exposure develop the disease. This indicates that other factors may be involved in determining whether someone gets mesothelioma or doesn't. For instance, you could inherit a predisposition to cancer or some other condition could increase your risk.

Other factors that may increase the risk of mesothelioma include:

  • Personal history of asbestos exposure. If you've been directly exposed to asbestos fibers at work or at home, your risk of mesothelioma is greatly increased.
  • Living with someone who works with asbestos. People who are exposed to asbestos may carry the fibers home on their skin and clothing. Exposure to these stray fibers over many years can put others in the home at risk of mesothelioma. People who work with high levels of asbestos can reduce the risk of bringing home asbestos fibers by showering and changing clothes before leaving work.
  • A family history of mesothelioma. If your parent, sibling or child has mesothelioma, you may have an increased risk of this disease.

Prevention - Malignant pleural mesothelioma

Reducing your exposure to asbestos may lower your risk of mesothelioma. Most people with mesothelioma were exposed to the asbestos fibers at work. Workers who may encounter asbestos fibers include:

  • Miners
  • Factory workers
  • Insulation manufacturers
  • Ship builders
  • Construction workers
  • Auto mechanic

Older homes and buildings may contain asbestos. In many cases, it's more dangerous to remove the asbestos than it is to leave it intact. Breaking up asbestos may cause fibers to become airborne, where they can be inhaled. Consult experts trained to detect asbestos in your home. These experts may test the air in your home to determine whether the asbestos is a risk to your health. Don't attempt to remove asbestos from your home, hire a qualified expert.

Diagnosis - Malignant pleural mesothelioma

If you have signs and symptoms that might indicate mesothelioma, your doctor will conduct a physical exam to check for any lumps or other unusual signs.

Once mesothelioma is diagnosed, your doctor orders other tests to determine the extent, or stage, of the cancer. Imaging tests that may help determine the stage of your cancer may include:

  • CT scans of the chest and abdomen
  • Magnetic resonance imaging (MRI)
  • Positron emission tomography (PET)

Your doctor determines which tests are more appropriate for you. Not every person needs every test.

Once the extent of pleural mesothelioma is determined, a stage is assigned.

  • Stage I mesothelioma is considered localized cancer, meaning it's limited to one portion of the lining of the chest.
  • Stage II mesothelioma may have spread beyond the lining of the chest to the diaphragm or to a lung.
  • Stage III mesothelioma may have spread to other structures within the chest and may involve nearby lymph nodes.
  • Stage IV mesothelioma is an advanced cancer that has spread more extensively within the chest. Stage IV may also indicate that mesothelioma has spread to distant areas of the body, such as the brain, liver and lymph nodes elsewhere in the chest.

Prognosis - Malignant pleural mesothelioma

Prognosis will depend on your general condition and stage of disease. The prognosis for malignant mesothelioma remains disappointing, although there have been some modest improvements from newer chemotherapies and multimodality treatments. Treatment of malignant mesothelioma at earlier stages has a better prognosis, but cures are exceedingly rare.

Treatment - Malignant pleural mesothelioma

Surgery: 

Surgeons work to remove mesothelioma when it's diagnosed at an early stage. In some cases this may cure the cancer. Sometimes it isn't possible to remove all of the cancer. In those cases, surgery may help to reduce the signs and symptoms caused by mesothelioma spreading in your body. Surgical options may include:

  • Surgery to decrease fluid buildup. Pleural mesothelioma may cause fluid to build up in your chest, causing difficulty breathing. Surgeons insert a tube or catheter into your chest to drain the fluid. Doctors may also inject medicine into your chest to prevent fluid from returning (pleurodesis).
  • Surgery to remove the tissue around the lungs or abdomen. Surgeons may remove the tissue lining the ribs and the lungs (pleurectomy) or the tissue lining the abdominal cavity (peritonectomy). This procedure won't cure mesothelioma, but may relieve signs and symptoms.
  • Surgery to remove as much of the cancer as possible (debulking). If all of the cancer can't be removed, surgeons may attempt to remove as much as possible. Debulking allows doctors to more accurately direct radiation treatments to relieve pain and fluid buildup caused by mesothelioma.
  • Surgery to remove a lung and the surrounding tissue.Removing the affected lung and the tissue that surrounds it may relieve signs and symptoms of pleural mesothelioma. If you'll be receiving radiation therapy to the chest after surgery, this procedure also allows doctors to use higher doses, since they won't need to worry about protecting your lung from damaging radiation.

Radiation:

For patients with localized disease, and who can tolerate a radical surgery, radiation can be given post-operatively as a consolidative treatment. The entire hemi-thorax is treated with radiation therapy, often given simultaneously with chemotherapy. Delivering radiation and chemotherapy after a radical surgery has led to extended life expectancy in selected patient populations. It also can induce severe side-effects, including fatal pneumonitis. As part of a curative approach to mesothelioma, radiotherapy is commonly applied to the sites ofchest drain insertion, in order to prevent growth of the tumor along the track in the chest wall.

Although mesothelioma is generally resistant to curative treatment with radiotherapy alone, palliative treatment regimens are sometimes used to relieve symptoms arising from tumor growth, such as obstruction of a major blood vessel. Radiation therapy when given alone with curative intent has never been shown to improve survival from mesothelioma. The necessary radiation dose to treat mesothelioma that has not been surgically removed would be very toxic.
Chemotherapy:

Chemotherapy uses chemicals to kill cancer cells. Systemic chemotherapy travels throughout the body and may shrink or slow the growth of a mesothelioma that can't be removed using surgery. Chemotherapy may also be used before surgery (neoadjuvant chemotherapy) to make an operation easier or after surgery (adjuvant chemotherapy) to reduce the chance that cancer will return. Chemotherapy drugs may also be heated and administered directly into the abdominal cavity (intraperitoneal chemotherapy), in the case of peritoneal mesothelioma. Using this strategy, chemotherapy drugs can reach the mesothelioma directly without injuring healthy cells in other parts of the body. This allows doctors to administer higher doses of chemotherapy drugs.

Approved therapies:

  • Pemetrexed disodium (Alimta) - FDA-approved indication: Treatment of patients with malignant pleural mesothelioma whose disease is either unresectable or who are otherwise not candidates for curative surgery
  • Belomycin sulfate (Blenoxane) - FDA approved indication: Treatment of malignant pleural effusion

 

Resources - Malignant pleural mesothelioma

Refer to Research Publications.

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Research Publications