All About Mesothelioma
What is mesothelial tissue?
The mesothelium is a protective sac that covers and protects most internal organs in the body. It is made of two layers; one layer covers the organ and the second layer forms a sac around it. The mesothelium makes a lubricating fluid that is released between these layers, allowing moving organs (such as the lungs) to move easily. This area, between the two layers around the lungs, is called the pleural space. Mesothelial tissue is found lining the abdominal cavity organs, lungs, testes, and heart.
What is mesothelioma?
Mesothelioma is a cancer of the mesothelial cells and happens when the mesothelial cells grow out of control. These cells also stop making lubricating fluid. As a result, organs are covered in thick tumor tissue and excess fluid buildup. This causes symptoms of mesothelioma. These cells can grow and invade other organs or spread to other areas of the body. When the cells spread to other areas of the body, it is called metastasis.
The majority (about 80%) of mesotheliomas are found in the lining of the lung. About 20% percent of cases are found in the abdominal cavity lining (peritoneal mesothelioma), and even more rarely, mesothelioma is found in the lining of the heart (1%) or testicles
What causes mesothelioma and am I at risk?
Mesothelioma is a rare cancer, with about 3,000 cases diagnosed each year in the United States. The biggest risk factor for developing the disease is exposure to asbestos. Asbestos exposure leads to 70 to 80 percent of all cases. Asbestos has been used in many products, including cement, brake linings, roof shingles, flooring products, textiles, and insulation. When making these products, asbestos particles can be released and inhaled.
Before knowing the dangers, asbestos miners and other workers exposed to asbestos did not wear any protection. Since the 1970s, the U.S. Occupational Safety and Health Administration (OSHA) has set limits for acceptable levels of asbestos exposure and requires protective equipment in the workplace. Family members of people who worked with asbestos may also have been exposed to the toxin when it was carried home on clothing and hair. This has put them at higher risk as well. It is five times more common in men, which is due in most part to work-related exposure to asbestos. Risk also increases with age.
Veterans who served in mining, milling, shipyard work, insulation work, demolition of old buildings, and other construction settings are at a higher risk for developing mesothelioma. Veterans who serve in countries where asbestos is still present in buildings damaged in combat are also at a higher risk to develop mesothelioma. Veterans with a diagnosis of mesothelioma may file a service claim for disability compensation if they believe their diagnosis is a direct result of service-connected asbestos exposure. These cases are determined on a case-by-case basis, but decisions can greatly impact your access to and the payment for medical care for mesothelioma.
While up to 80% of cases of pleural mesothelioma happen in people who have had known asbestos exposure, only 10% of those with a history of heavy exposure get the disease. It is possible that additional exposures or factors are involved to actually develop the disease. Only 50% of people with peritoneal mesothelioma have a history of asbestos exposure.
It takes 10 to 50 years from the time of asbestos exposure until mesothelioma is found. Of those diagnosed, some had repeated exposure to asbestos over many years or longer and some had as little as one or two months of asbestos exposure.
The rate of mesothelioma is different around the world and depends on when asbestos was widely used in that area. Rates are higher in the United Kingdom. Asbestos use in Western Europe remained high until 1980, whereas maximum exposure in the U.S. was from the 1930s to the 1960s. Australia was one of the world's largest producers of asbestos, leading to the country having the highest rates worldwide (based on the size of the population). Rates in the U.S. are beginning to decline, whereas rates in Europe and Australia should plateau in the next 10-15 years, before declining.
Following the ban of asbestos in many countries, asbestos producers started to promote the sale of their products to developing countries, such as Asia and Latin America. Experts fear that the peak rates in these areas are yet to come, and will be similar to what has been seen in the U.S. and Europe. Asbestos is still widely available, even today. In countries like China and India, where it is still used cases of mesothelioma are projected to increase greatly over the next two decades.
Other risk factors include prior radiation therapy to the chest, collapse therapy (for the treatment of tuberculosis), and potential exposure to certain viruses or zeolites (minerals that have a chemical similarity to asbestos such as erionite). Erionite is a known human carcinogen and is common in rocks and soil in certain geographic areas. Higher mesothelioma rates in these areas are thought to be caused by increased exposure to erionite. Smoking does not seem to increase the risk of developing the disease unless you were also exposed to asbestos.
How can I prevent mesothelioma?
You can prevent mesothelioma by not being exposed to asbestos. Workers who are exposed to asbestos on the job should wear protective clothing and masks. They should change their clothing before leaving the worksite to avoid carrying any particles home. OSHA has set standards regulating these workplace rules and protections.
What screening tests are used for mesothelioma?
There is no good screening test for mesothelioma. Radiology tests like x-rays and CT scans are not able to find these tumors before symptoms occur. Researchers are studying the use of several blood markers in an attempt to detect mesothelioma earlier than conventional methods for people with a history of asbestos exposure. These tests include Fibulin-3 and soluble mesothelin-related peptides (SMRP’s). These blood tests alone cannot diagnosis mesothelioma and still need further research to study how well they are at predicting risk for developing mesothelioma.
What are the signs of mesothelioma?
The symptoms of mesothelioma are often caused by a build-up of tumor tissue surrounding the lung and a build-up of fluid in the pleural space. This prevents the lung from expanding (opening) fully. This causes pressure on the lung, leading to chest pain and shortness of breath. As the disease progresses, you may lose weight and have a dry, hacking cough. Mesothelioma that starts in the pleura can directly spread into the abdomen.
Mesothelioma can also start in the peritoneal tissue of the abdomen. Symptoms of abdominal mesothelioma include abdominal swelling, pain, and weight loss.
How is mesothelioma diagnosed?
If your provider thinks you may have mesothelioma, they will order tests. The chest x-ray of a person with pleural mesothelioma often will show a build-up of fluid in the lining of the lung. If this is found a CT scan of the chest will be done to better look at the lungs. For abdominal mesothelioma, a CT scan is done to look at the organs in the abdomen.
A thoracentesis is a procedure done to remove the buildup of fluid. This can be done to diagnose mesothelioma or to improve symptoms. A diagnosis of mesothelioma can be made by looking at the cells of this fluid under the microscope. If a diagnosis is not possible with the fluid alone, you would then have a pleural biopsy. During this procedure, a thoracoscope (thin tube with a small camera on it) is used to go through the chest wall, between the ribs, to obtain a sample of the tissue. A peritoneoscope or abdominal laparoscopy is used to enter the abdomen to obtain a tissue sample to diagnose abdominal mesothelioma.
Other tests used in the diagnosis and staging of mesothelioma include a chest and abdominal CT with contrast and chest MRI or VATS (thoracoscopic biopsy). These tests can also look at lymph nodes and other tissues. A pathologist will examine the cells/tissues to determine the subtype of mesothelioma cells present in the tumor. There are three types of cells, epithelioid, sarcomatoid, and biphasic (mixed). The cell subtype can help stage and decide which treatments are best.
How is mesothelioma staged?
After these tests are done, the cancer is staged. Staging provides information about the extent and possible spread of the disease as well as helps to guide treatment planning. The staging system used to describe pleural mesothelioma is the "TNM system,” as described by the American Joint Committee on Cancer. The TNM systems are used to describe many types of cancers. They have three parts
- T-describes the size/location/extent of the "primary" tumor in the lung.
- N-describes if the cancer has spread to the lymph nodes.
- M-describes if the cancer has spread to other organs (metastases).
The staging system is very complex. The entire staging system is outlined at the end of this article. Though complicated, the staging system helps healthcare providers determine the extent of the cancer, and in turn, make treatment decisions for your cancer. There is currently no standard staging system for peritoneal mesothelioma.
How is mesothelioma treated?
Treatment depends on the stage of the disease, the location of the tumor, your age, and your health status. Your provider will talk to you about your treatment options.
The first step to deciding on treatment is to determine if the disease is operable. Younger, healthy patients with early-stage malignant pleural mesothelioma may be able to have surgery that removes the mesothelial tissue around the tumor. Surgery to either remove the entire lung with the tumor (termed extrapleural pneumonectomy) or lung-sparing surgery that removes only the tumor and the lining of the lung (termed extended or radical pleurectomy), is the most common option for these patients.
Surgery may also be an option for patients with peritoneal mesothelioma. Patients with peritoneal mesothelioma may also receive intraperitoneal chemotherapy (chemotherapy delivered directly into the peritoneal space) with surgery. This has been shown to improve outcomes in patients with peritoneal mesothelioma.
Surgery for mesothelioma is only for patients who are healthy enough to have the surgery. Those with advanced disease may not be able to tolerate surgery.
Radiation is the use of high-energy x-rays to kill cancer cells. Radiation therapy is often done after surgery to remove the entire lung to kill any remaining cancer cells. Radiation therapy after lung-sparing surgery is not routinely given. The radiation can damage the healthy lung tissue and result in side effects that outweigh any benefit of radiation. Radiation therapy is often delivered to surgical incision sites to prevent the cancer from recurring (coming back) in that area. In patients who do not undergo surgery, radiation therapy may be given to treat problem areas with the goal of relieving symptoms (called palliative radiation), like pain or trouble breathing.
Chemotherapy is the use of medications to kill cancer cells and is a common treatment for mesothelioma. It can provide symptom relief. Chemotherapy can be given before, after, or without surgery. Medications that are used, either alone or in combination, include cisplatin, carboplatin, doxorubicin, pemetrexed, gemcitabine, nivolumab, ipilimumab, pembrolizumab, and vinorelbine.
Symptom Management and Supportive Care
Mesothelioma can cause a recurring build-up of fluid in the pleural space. This fluid can be removed with:
- Pleural Catheter - A tube is put into the chest wall and left in to allow the fluid to be drained when needed.
- Thoracentesis – A procedure that uses a small needle that is put through the chest wall into the pleural space, drains the fluid, and then the needle is removed. In many cases, thoracentesis will be followed by a procedure called pleurodesis. During pleurodesis, a medication (i.e. talc, bleomycin) is injected into the lung to create scar tissue. This is thought to decrease fluid from developing.
In the abdomen, the procedure to remove fluid is called paracentesis. A needle is inserted through the abdomen into the fluid-filled space, and the fluid is drained. If this is a chronic problem, patients may have a catheter placed, allowing them to drain the fluid themselves at home as needed. Removal of the fluid helps the patient breathe better and lessens pain that is caused by fluid build-up.
There are ways to treat symptoms including pain, nausea, and vomiting you may have. These symptoms can be managed through the use of medical treatments (i.e. pain medications, anti-nausea medication, and counseling) and integrative therapies (i.e. yoga, mindfulness, reiki, and massage). You should also talk with your healthcare team about the role of palliative care in your treatment plan. Palliative care can help relieve side effects and symptoms of illness.
Because the current therapies have limited effectiveness, researchers are continuing to look for new ways to treat mesothelioma. Some of the treatments being investigated include immunotherapy, gene therapy (a method that attempts to correct the abnormal gene that causes the cancer to grow out of control), chemotherapy administered directly into the pleural space, alternating electric fields/tumor treating fields (mild electric currents passed through electrodes attached to your chest/back that are thought to affect tumor cells), and intraoperative Photodynamic Therapy (PDT- a treatment that uses a laser to activate a photosensitizing drug during the surgical removal of the cancer in an attempt to kill any remaining cancer cells not removed by surgery). Patients should talk with their healthcare team about current clinical trials for mesothelioma. You can also explore currently open clinical trials using the OncoLink Clinical Trial Matching Service.
Follow-up Care and Survivorship
Your healthcare team will provide regular physical examinations and surveillance imaging throughout your treatment for mesothelioma.
Fear of advanced illness, anxiety, advanced care planning, the financial impact of cancer treatment, legal and employment issues, and coping strategies are common emotional and practical issues experienced by people with mesothelioma. Your healthcare team can identify resources for support and management of these practical and emotional challenges faced during and after cancer.
Cancer survivorship is a relatively new focus of oncology care. With nearly 17 million cancer survivors in the US alone, there is a need to help patients transition from active treatment to survivorship. What happens next, how do you get back to normal, what should you know and do to live healthy going forward? A survivorship care plan can be a first step in educating yourself about navigating life after cancer and helping you communicate knowledgeably with your healthcare providers. Create a survivorship care plan today on OncoLink.
Resources for More Information
Department of Veterans Affairs www.publichealth.va.gov/exposures/asbestos/
The Meso Foundation (formerly the Mesothelioma Applied Research Foundation) www.curemeso.org/site/c.duIWJfNQKiL8G/b.8598593/k.D685/Homepage.htm
Resources for More Information
Appendix: Complete Staging System for Malignant Pleural Mesothelioma
AJCC, Cancer Staging Manual, 8th Edition
*There is currently no standard staging system for peritoneal mesothelioma.
Primary Tumor (T)
Primary tumor cannot be assessed
No evidence of primary tumor
Tumor limited to the ipsilateral parietal pleura with or without involvement of:
Tumor involving each of ipsilateral pleural surfaces (parietal, mediastinal, diaphragmatic, and visceral pleura) with at least one of the following:
Locally advanced but potentially resectable tumor. Tumor involving all of the ipsilateral pleural surfaces (parietal, mediastinal, diaphragmatic, and visceral pleura), with at least one of the following:
Locally advanced technically unresectable tumor. Tumor involving all of the ipsilateral pleural services (parietal, mediastinal, diaphragmatic, and visceral pleura) with at least one of the following:
Select if synchronous primary tumors are found in single organ.
Regionals Lymph Nodes (N)
Regional lymph nodes cannot be assessed
No regional lymph node metastasis
Metastases in the ipsilateral bronchopulmonary, hilar, or mediastinal (including the internal mammary, peridiaphragmatic, pericardial fat pad, or intercostal) lymph nodes
Metastases in the contralateral mediastinal, ipsilateral, or contralateral supraclavicular lymph nodes
Select if regional lymph node metastasis identified by SLN biopsy only.
Select if regional lymph node metastasis identified by FNA or core needle biopsy only.
Distant Metastasis (M)
No distant metastasis
Distant metastasis, microscopically confirmed
T2 or 3
T 1 or 2
T 1, 2 or 3
Grade of differentiation cannot be assessed
Lymphovascular Invasion (LVI)
LVI not present (absent)/not identified
LVI present/identified, NOS
Lymphatic and small vessel invasions only (L)
Venous (large vessel) invasion only (V)
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