There is always research going on in the area of mesothelioma. Scientists are looking for better ways to prevent, diagnose, and treat mesothelioma. Despite recent progress, much remains to be learned about the best way to treat these cancers.

Causes and prevention

Some research is focused on learning exactly how asbestos changes mesothelial cells and their DNA to cause these cancers. Understanding how these fibers produce cancer might help us develop ways to prevent those changes.

The role of asbestos in increasing the risk of mesothelioma is a definite public health concern. Researchers are learning more about which asbestos fibers can cause cancer, how they cause it, and what levels of exposure might be considered safe. Now that the dangers of asbestos are known, we can limit or stop exposure in homes, public buildings, and the workplace. Unfortunately, regulations protecting workers from asbestos exposure are much less stringent in some countries than in others.

Research is also under way to clarify the role (if any) of SV40, a virus that has been linked to mesothelioma in some studies.

Treatment

Mesothelioma remains a difficult cancer to treat, and doctors are constantly trying to improve on current approaches. The exact roles of surgery, radiation therapy, and chemotherapy in the treatment of mesothelioma are still being studied. Combinations of these treatments are now being tested and may provide the most promising option for some patients. Newer types of treatment now being studied may give patients and their doctors even more options.

Chemotherapy

Some chemotherapy drugs can shrink or slow the growth of mesotheliomas, but in most cases the effects last for a limited time. Studies are underway to test newer chemotherapy drugs.

Photodynamic therapy

Another technique now being studied is photodynamic therapy (PDT). For this treatment, a light-activated drug is injected into a vein. The drug spreads throughout the body and tends to collect in cancer cells. A few days later (usually in the operating room, just after surgery), a special red light on the end of a tube is placed into the chest. The light causes a chemical change that activates the drug and kills the cancer cells. Since the drug is only active in the areas exposed to the special light, this approach might cause fewer side effects than using drugs that spread throughout the body. Several clinical trials are now studying the use of PDT for mesothelioma. To find out more about PDT, see Photodynamic Therapy.

Targeted drugs

In general, chemo drugs have a limited effect against mesothelioma. As researchers have learned more about the changes in cells that cause cancer, they have developed newer drugs that target these changes. Targeted drugs work differently from standard chemo drugs. They sometimes work when chemo drugs don’t, and they often have different (and less severe) side effects.

Sunitinib (Sutent) is an example of a targeted drug that has shown promise in some studies.

Other new drugs have different targets. For example, some new drugs target mesothelin, a protein found in high levels in mesothelioma cells. To learn more about targeted therapy drugs, see Targeted Therapy.

Other newer forms of treatment

Because standard treatments often have limited usefulness against mesothelioma, researchers are studying other new types of treatment as well.

Gene therapy: A newer type of treatment being tested on mesothelioma is gene therapy, which attempts to add new genes to cancer cells to make them easier to kill. One approach to gene therapy uses special viruses that have been modified in the lab. The virus is injected into the pleural space and infects the mesothelioma cells. When this infection occurs, the virus injects the desired gene into the cells. In one version of this approach, the virus carries a gene that helps turn on the immune system to attack the cancer cells. Early studies of this approach have found it may shrink or slow the growth of mesothelioma in some people, but more research is needed to confirm this.

Immunotherapy: Other new treatments called cancer vaccines are also aimed at getting the immune system to attack the cancer. In one approach, immune cells are removed from a patient’s blood and treated in the lab to get them to react to tumor cells. The immune cells are then given back to the patient as blood transfusions, where it is hoped they will cause the body’s immune system to attack the cancer. This approach is now being studied in clinical trials.

Another form of immunotherapy being studied is a drug called tremelimumab, which targets a certain immune cells and takes the brakes off the immune system.

To learn more, see Cancer Immunotherapy.

Virus therapies: Researchers are also studying the use of specially designed viruses to treat mesothelioma. These viruses can be put into the pleural space, where the hope is that they can either infect and kill the cancer cells directly, or cause the immune system to attack the cancer cells. These approaches are still in the early phases of clinical trials.

Mesothelioma is most often diagnosed after a person goes to a doctor because of symptoms they are having. If there is a reason to suspect you might have mesothelioma, your doctor will examine you and use one or more tests to find out. Symptoms might suggest that the problem could be mesothelioma, but tests will be needed to confirm the diagnosis.

Medical history and physical exam

If you have any signs or symptoms that suggest you might have mesothelioma, your doctor will want to get your medical history to learn about your symptoms and possible risk factors, especially asbestos exposure.

A physical exam can provide information about possible signs of mesothelioma and other health problems. Pleural mesothelioma can cause fluid to build up around the lungs in the chest (called a pleural effusion). In cases of peritoneal mesothelioma, fluid can build up in the abdomen (called ascites). In pericardial mesothelioma, fluid builds up in the sac around the heart (called a pericardial effusion). Rarely, mesothelioma can develop in the groin and look like a hernia. All of these might be found during a physical exam, such as when the doctor listens to these areas with a stethoscope or taps on the chest or abdomen.

If mesothelioma is a possibility, tests will be needed to make sure. These might include imaging tests, blood tests, and other procedures.

Imaging tests

Imaging tests use x-rays, radioactive particles, sound waves, or magnetic fields to create pictures of the inside of your body. Imaging tests might be done for a number of reasons, such as:

• To look at suspicious areas that might be cancer
• To learn how far cancer has spread
• To help determine if treatment is working

People thought to have mesothelioma may have one or more of these tests.

Chest x-ray

This is often the first test done if someone has symptoms such as a constant cough or shortness of breath. Findings that might suggest mesothelioma include an abnormal thickening of the pleura, calcium deposits on the pleura, fluid in the space between the lungs and the chest wall, or changes in the lungs themselves as a result of asbestos exposure.

Computed tomography (CT) scan

The CT scan uses x-rays to make detailed cross-sectional images of your body. Instead of taking one picture, like a regular x-ray, a CT scanner takes many pictures as it rotates around you while you are lying on a narrow table. A computer then combines these into images of slices of the body.

CT scans are often used to help look for mesothelioma and to determine the exact location of the cancer. They can also help determine the stage (extent) of the cancer. For example, they can show if the cancer has spread to other organs. This can help determine if surgery might be a treatment option. Finally, CT scans can also be used to learn if treatment such as chemotherapy is shrinking or slowing the growth of the cancer.

A CT scanner has been described as a large donut, with a narrow table that slides in and out of the middle opening. You will need to lie still on the table while the scan is being done. CT scans take longer than regular x-rays, and you might feel a bit confined by the ring while the pictures are being taken.

Before the test, you might have to drink a liquid called oral contrast. This helps outline the intestine so that certain areas are not mistaken for tumors. You might also need an IV (intravenous) line through which a different kind of contrast is injected. This helps better outline structures in your body. The injection can cause some flushing (redness and warm feeling). Some people are allergic and get hives or, rarely, more serious reactions like trouble breathing and low blood pressure. Be sure to tell the doctor if you have any allergies (especially to iodine or shellfish) or have ever had a reaction to any contrast material used for x-rays.

Echocardiogram

This test uses sound waves to look at the heart. It may be done if your doctor suspects that you have fluid around your heart (a pericardial effusion). This test can also tell how well the heart is working. For the most common version of this test, you lie on a table while a technician moves an instrument called a transducer over the skin on your chest. A gel is often put on the skin first.

Positron emission tomography (PET) scan

For a PET scan, a radioactive substance (usually a type of sugar related to glucose, known as FDG) is injected into the blood. The amount of radioactivity used is very low. Because cancer cells grow quickly, they absorb more of the sugar than most other cells. After waiting about an hour, you lie on a table in the PET scanner for about 30 minutes while a special camera creates a picture of areas of radioactivity in the body.

The picture from a PET scan is not as detailed as a CT or MRI scan, but it can provide helpful information about whether abnormal areas seen on these tests are likely to be cancerous or not. For example, it can give the doctor a better idea of whether a thickening of the pleura or peritoneum seen on a CT scan is more likely cancer or merely scar tissue. If you have been diagnosed with mesothelioma, your doctor may use this test to see if the cancer has spread to lymph nodes or other parts of the body. A PET scan can also be useful if your doctor thinks the cancer may have spread but doesn’t know where.

Some machines can do both a PET and CT scan at the same time (PET/CT scan). This lets the doctor compare areas of higher radioactivity on the PET scan with the more detailed appearance of that area on the CT.

Magnetic resonance imaging (MRI) scan

Like CT scans, MRI scans make detailed images of the body’s soft tissues. But MRI scans use radio waves and strong magnets instead of x-rays. A contrast material called gadolinium is often injected into a vein before the scan to better show details. This contrast is different than the one used for CT scans, so being allergic to one doesn’t mean you are allergic to the other.

MRI scans can sometimes help show the exact location and extent of a tumor since they provide very detailed images of soft tissues. For mesotheliomas, they may be useful in looking at the diaphragm (the thin band of muscle below the lungs that helps us breathe), a possible site of cancer spread.

MRI scans take longer than CT scans – often up to an hour. You may have to lie inside a narrow tube, which can upset people with a fear of enclosed spaces. Special, more open MRI machines may be an option in some cases. The MRI machine makes buzzing and clicking noises that you might find disturbing. Some places will give you earplugs to help block this out.

Blood tests

Blood levels of certain substances are often higher in people with mesothelioma:

• Osteopontin
• Soluble mesothelin-related peptides (SMRPs), detected with the MesoMark^® test

Mesothelioma can’t be diagnosed with these blood tests alone, but high levels of these substances can make the diagnosis more likely. These tests are not routinely used in most doctors’ offices because of their limited value.

Tests of fluid and tissue samples

Symptoms and test results may strongly suggest that a person has mesothelioma, but the actual diagnosis is made by removing cells from an abnormal area and looking at them under a microscope. This is known as a biopsy. It can be done in different ways, depending on the situation.

Removing fluid for testing

If there is a buildup of fluid in part of the body that might be due to mesothelioma, a sample of this fluid can be removed by inserting a thin, hollow needle through the skin and into the fluid. Numbing medicine is used on the skin before the needle is inserted. This may be done in a doctor’s office or in the hospital. Sometimes ultrasound (or an echocardiogram) is used to guide the needle. These tests use sound waves to see inside the body.

This procedure has different names depending on where the fluid is:

• Thoracentesis removes fluid from the chest.
• Paracentesis removes fluid from the abdomen.
• Pericardiocentesis removes fluid from the sac around the heart.

The fluid is then tested for its chemical makeup and is looked at under a microscope to see if it contains cancer cells. If cancer cells are found, special tests might be done to see if the cancer is a mesothelioma, a lung cancer, or another type of cancer.

Even if no cancer cells are found in the fluid, a person might still have cancer. In many cases, doctors need to get an actual sample of the mesothelium (the pleura, peritoneum, or pericardium) to determine if a person has mesothelioma.

Needle biopsies

Suspected tumors in the chest are sometimes sampled by needle biopsy. A long, hollow needle is passed through the skin in the chest between the ribs and into the pleura. Imaging tests such as CT scans are used to guide the needle into the tumor so that small samples can be removed to be looked at under the microscope. This is often done using just numbing medicine.

Needle biopsy can also be used to get samples of the lymph nodes in the space between the lungs to see if the cancer has spread there (see “Endobronchial ultrasound needle biopsy”).

Needle biopsies do not require a surgical incision or overnight hospital stay. But the downside is that sometimes the samples removed are not big enough to make an accurate diagnosis. This is especially true for mesothelioma. A more invasive biopsy method may be needed.

There is a slight chance that the needle could put a small hole in the lung during the biopsy. This can cause air to build up in the space between the lung and the chest wall (known as a pneumothorax). A small pneumothorax might not cause any symptoms. It may only be seen on an x-ray done after the biopsy, and it will often go away on its own. But a larger pneumothorax can make part of a lung collapse and might need to be treated. The treatment is placement of a small tube (a catheter) through the skin and into the space between the lungs. The tube is used to suck the air out in order to re-expand the lung and is left in place for a short time.

Endoscopic biopsies

Endoscopic biopsy is commonly used to diagnose mesothelioma. An endoscope is a thin, tube-like instrument used to look inside the body. It has a light and a lens (or tiny video camera) on the end for viewing and often has a tool to remove tissue samples. Endoscopes have different names depending on the part of the body where they’re used.

Thoracoscopy: This procedure uses an endoscope called a thoracoscope to look at areas inside the chest. It can be used to look at the pleura and take tissue samples for biopsies.

Thoracoscopy is done in the operating room while you are under general anesthesia (in a deep sleep). The doctor inserts the thoracoscope through one or more small cuts made in the chest wall to look at the space between the lungs and the chest wall. This lets the doctor see possible areas of cancer and remove small pieces of tissue to look at under the microscope. The doctor can also sample lymph nodes and fluid and see if a tumor is growing into nearby tissues or organs.

Thoracoscopy can also be used as part of a procedure to keep fluid from building up in the chest. This is called pleurodesis and is discussed in Palliative Procedures Used for Malignant Mesothelioma.

Laparoscopy: For this test, the doctor uses an endoscope called a laparoscope to look inside the abdomen and biopsy any peritoneal tumors. This is done in the operating room while you are under general anesthesia (in a deep sleep). The laparoscope is inserted into the abdomen through small cuts on the front of the abdomen.

Mediastinoscopy: If imaging tests such as a CT scan suggest that the cancer might have spread to the lymph nodes between the lungs, the doctor may want to sample some of them to see if they really contain cancer. The area between the lungs is called the mediastinum, and looking at it with an endoscope is called mediastinoscopy. This is done in an operating room while you are under general anesthesia (in a deep sleep).

A small cut is made in the front of the neck above the breastbone (sternum) and a thin, hollow, lighted tube (called a mediastinoscope) is inserted behind the sternum. Special instruments can be passed through this tube to take tissue samples from the lymph nodes along the windpipe and the major bronchial tube areas.

Lung cancers often spread to lymph nodes, but mesotheliomas do this less often. Testing the lymph nodes can help show whether a cancer is still localized or if it has started to spread, which might affect treatment options. It can also sometimes help tell lung cancers from mesotheliomas.Patients with mesothelioma don’t need to have bronchoscopy to see if tumors are in their airways (because that isn’t where tumors from mesothelioma are found). Instead, bronchoscopy may be used to biopsy lymph nodes near the lungs (instead of using mediastinoscopy).

Endobronchial ultrasound needle biopsy: For this test, a bronchoscope (a long, thin, flexible, fiber-optic tube) with an ultrasound device at its tip is passed down the throat and into the windpipe. The ultrasound lets the doctor see the nearby lymph nodes. A hollow needle is then passed down the bronchoscope and through the airway wall into the nodes to take biopsy samples. This procedure may be done with either general anesthesia (where you are asleep), or with numbing medicine (local anesthesia) and light sedation.

Open surgical biopsy

Sometimes, endoscopic biopsies aren’t enough to make a diagnosis, so more invasive procedures are needed. By making an incision in the chest (thoracotomy) or an incision in the abdomen (laparotomy) the surgeon can remove a larger sample of tumor or, sometimes, remove the entire tumor.

Testing the samples in the lab

No matter how they’re obtained, all biopsy and fluid samples are sent to the pathology lab. There, a doctor will look at them under a microscope and test them to find out if they contain cancer cells (and if so, what type of cancer it is).

It’s often hard to diagnose mesothelioma by looking at cells from fluid samples. It can even be hard to diagnose mesothelioma with tissue from small needle biopsies. Under the microscope, mesothelioma can often look like other types of cancer. For example, pleural mesothelioma can resemble some types of lung cancer, and peritoneal mesothelioma in women may look like some cancers of the ovaries.

For this reason, special lab tests are often done to help tell mesothelioma from some other cancers. To learn about some of the tests that might be done on tissue samples, see Testing Biopsy and Cytology Specimens for Cancer.

If mesothelioma is diagnosed, the doctor will also determine what type of mesothelioma it is, based on the patterns of cells seen in the microscope. Most mesotheliomas are classified as either epithelioid, sarcomatoid, or mixed/biphasic.

Pulmonary function tests

If mesothelioma has been diagnosed, pulmonary function tests (PFTs) may be done to see how well your lungs are working. This is especially important if surgery might be an option to treat the cancer. Surgery often requires removing part or all of a lung, so it’s important to know how well the lungs are working to start with. These tests can give the surgeon an idea of whether surgery may be an option, and if so, how much lung can safely be removed safely.

There are a few different types of PFTs, but they all basically have you breathe in and out through a tube connected to a machine that measures your lung function.

After someone is diagnosed with malignant mesothelioma, doctors will try to figure out if it has spread, and if so, how far. This process is called staging. The stage of a cancer describes how much cancer is in the body. It helps determine how serious the cancer is and how best to treat it. Doctors also use a cancer's stage when talking about survival statistics.

The stages of mesothelioma range from I (1) through IV (4). As a rule, the lower the number, the less the cancer has spread. A higher number, such as stage IV, means cancer has spread more. And within a stage, an earlier letter means a lower stage. Although each person’s cancer experience is unique, cancers with similar stages tend to have a similar outlook and are often treated in much the same way.

How is the stage determined?

Malignant pleural mesothelioma (MPM), the most common type, is the only mesothelioma for which a formal staging system exists. These mesotheliomas start in the pleura, which includes the lining of the lungs and the inner lining of the chest wall.

The staging system most often used for MPM is the American Joint Committee on Cancer (AJCC) TNM system, which is based on 3 key pieces of information:

• The extent (size) of the main tumor (T): Has the cancer grown into nearby structures or organs? Is it possible to remove it with surgery?
• The spread to nearby lymph nodes (N): Has the cancer spread to nearby lymph nodes?
• The spread (metastasis) to distant sites (M): Has the cancer spread to distant organs such as the bones, the liver, the lung or pleura (lining of the lung) on the other side of the body, or the peritoneum (the lining of the abdomen)?

Numbers or letters after T, N, and M provide more details about each of these factors. Higher numbers mean the cancer is more advanced. Once a person’s T, N, and M categories have been determined, this information is combined in a process called stage grouping to assign an overall stage. For more information, see Cancer Staging.

The system described below is the most recent AJCC system, effective as of January 2018. It is used only for malignant pleural mesotheliomas. Mesotheliomas starting in other places are less common and do not have formal staging systems.

MPM is typically given a clinical stage based on the results of a physical exam, biopsy, and imaging tests (as described in How Is Malignant Mesothelioma Diagnosed?). If surgery is done, the pathologic stage (also called the surgical stage) is determined by examining tissue removed during the operation. 

Cancer staging can be complex, so ask your doctor to explain it to you in a way you understand.

Stages of malignant pleural mesothelioma

* The following additional categories are not listed on the table above: 

• TX: Main tumor cannot be assessed due to lack of information.
• T0: There is no evidence of a primary tumor.
• NX: Nearby lymph nodes cannot be assessed due to lack of information. 

Resectable versus unresectable cancer

The TNM system groups mesotheliomas into several stages that help give doctors an idea about a person’s prognosis (outlook). But for treatment purposes, doctors often use a simpler system, based on whether the cancer is likely to be resectable (where all visible tumor can be removed by surgery) or unresectable.

In general, most stage I and II mesotheliomas, as well as some stage III mesotheliomas, are potentially resectable, but there are exceptions. Whether the cancer can be removed depends not only on how far the tumor has grown, but also on its subtype (most doctors believe only epithelioid and mixed/biphasic tumors are potentially resectable), where it’s located, and if the patient is healthy enough to have surgery.

Even for resectable mesotheliomas, in most cases cancer cells that can’t be seen are left behind after surgery. For this reason, many doctors use other treatments (radiation therapy and/or chemotherapy) along with surgery when possible.

Other prognostic factors

Stage is an important factor in predicting a person’s prognosis (outlook), but other factors also play a role. Some factors linked to longer survival times include:

• Still being able to carry out normal daily tasks
• Being younger
• Being female
• Having the epthelioid subtype of mesothelioma
• Having normal levels of LDH in the blood
• Having normal levels of red blood cells, white blood cells, and platelets

Many of the early symptoms of mesothelioma are more likely to be caused by other conditions, so at first people may ignore them or mistake them for common, minor ailments. Most people with mesothelioma have symptoms for at least a few months before they are diagnosed.

Symptoms of pleural mesothelioma (mesothelioma of the chest) can include:

• Pain in the side of the chest or lower back
• Shortness of breath
• Cough
• Fever
• Excessive sweating
• Fatigue
• Weight loss (without trying)
• Trouble swallowing (feeling like food gets stuck)
• Hoarseness
• Swelling of the face and arms

Symptoms of peritoneal mesothelioma can include:

• Abdominal (belly) pain
• Swelling or fluid in the abdomen
• Weight loss (without trying)
• Nausea and vomiting
• Constipation

These symptoms can be caused by mesothelioma, but more often they are caused by other conditions. Still, if you have any of these problems (especially if you have been exposed to asbestos), it’s important to see your doctor right away so the cause can be found and treated, if needed.

If cancer keeps growing or comes back after one kind of treatment, it may be possible to try another treatment plan that might still cure the cancer, or at least keep it under control enough to help you live longer and feel better. Clinical trials also might offer chances to try newer treatments that could be helpful. But when many different treatments have been tried and the cancer is still growing, even newer treatments might no longer be helpful. If this happens, it’s important to weigh the possible limited benefits of a new treatment against the possible downsides, including treatment side effects. Everyone has their own way of looking at this.

This is likely to be the hardest part of your battle with cancer – when you have been through many treatments and nothing’s working anymore. Your doctor might offer you new options, but at some point you need to consider that treatment is not likely to improve your health or change your outcome or survival.

If you want to continue to get treatment for as long as you can, you need to think about the odds of treatment having any benefit and how this compares to the possible risks and side effects. Your doctor can estimate how likely it is the cancer will respond to treatment you’re considering. For instance, the doctor may say that more treatment might have about a 1 in 100 chance of working. Some people are still tempted to try this. But it’s important to have realistic expectations if you do choose this plan.

Palliative care

No matter what you decide to do, it’s important that you feel as good as you can. Make sure you are asking for and getting treatment for any symptoms you might have, such as nausea or pain. This type of treatment is called palliative care.

Palliative care helps relieve symptoms, but it’s not expected to cure the disease. It can be given along with cancer treatment, or can even be cancer treatment. The difference is its purpose – the main goal of palliative care is to improve the quality of your life, or help you feel as good as you can for as long as you can. Sometimes this means using drugs to help with symptoms like pain or nausea. Sometimes, though, the treatments used to control your symptoms are the same as those used to treat cancer. For instance, radiation or chemo might be used to help relieve pain caused by the cancer. But this is not the same as treatment to try to cure the cancer.

Hospice care

At some point, you may benefit from hospice care. This is special care that treats the person rather than the disease; it focuses on quality rather than length of life. Most of the time, it is given at home. Your cancer may be causing problems that need to be managed, and hospice focuses on your comfort. You should know that while getting hospice care often means the end of treatments such as chemo and radiation, it doesn’t mean you can’t have treatment for the problems caused by your cancer or other health conditions. In hospice the focus of your care is on living life as fully as possible and feeling as well as you can at this difficult time. To learn more about hospice, see Hospice Care.

Staying hopeful is important, too. Your hope for a cure may not be as bright, but there is still hope for good times with family and friends – times that are filled with happiness and meaning. Pausing at this time in your cancer treatment gives you a chance to refocus on the most important things in your life. Now is the time to do some things you’ve always wanted to do and to stop doing the things you no longer want to do. Though the cancer may be beyond your control, there are still choices you can make.

You can learn more about the changes that occur when curative treatment stops working, and about planning ahead for yourself and your family, see Nearing the End of Life and Advance Directives.

Mesothelioma is fairly rare in the United States, with about 3,000 new cases being diagnosed each year.

The rate of mesotheliomas in the United States increased from the 1970s to the early 1990s, but since then it has leveled off and even gone down slightly. These changes have largely been seen in men, and are probably related to changes over time in workplace exposures to asbestos. (See What Are the Risk Factors for Malignant Mesothelioma?) The rate of mesothelioma is lower in women and has been fairly steady for some time. In many other countries, the rate of mesothelioma is still increasing.

Mesothelioma is more common in whites and Hispanics/Latinos than in African Americans or Asian Americans.

Mesotheliomas are much more common in older people than younger people. The average age at the time of diagnosis for pleural mesothelioma (mesothelioma in the chest) is 69.

Information on survival rates can be found in Survival Statistics for Mesothelioma.

Visit the American Cancer Society’s Cancer Statistics Center for more key statistics.

A risk factor is anything that affects your chance of getting a disease such as cancer. Different cancers have different risk factors. Some risk factors, like smoking, can be changed. Others, like a person’s age or family history, can’t be changed.

But having a known risk factor, or even several, does not mean that you will get the disease. And some people who get the disease may have few or no known risk factors.

Researchers have found some factors that increase a person’s risk of mesothelioma.

Asbestos

The main risk factor for pleural mesothelioma is exposure to asbestos. In fact, most cases of pleural mesothelioma have been linked to asbestos exposure, usually from high levels of exposure in the workplace.

Asbestos is a group of minerals that occur naturally as bundles of tiny fibers. These fibers are found in soil and rocks in many parts of the world.

When asbestos fibers in the air are inhaled, they can get into the lungs. Fibers that stay in the lungs can travel to the ends of the small airways and enter the pleural lining of the lung and chest wall. These fibers can then injure the cells of the pleura, and eventually cause mesothelioma. Asbestos fibers can also damage cells of the lung and result in asbestosis (scar tissue in the lung) and/or lung cancer.

Peritoneal mesothelioma, which forms in the abdomen, can result from coughing up and swallowing inhaled asbestos fibers.

Many people are exposed to very low levels of naturally occurring asbestos in outdoor air in dust that comes from rocks and soil containing asbestos. This is more likely to happen in areas where rocks have higher asbestos content. In some areas, asbestos can be found in the water supply as well as in the air.

In the past, asbestos was used in many products because of its heat and fire-resistant properties. The link between asbestos and mesothelioma is now well known, so its use in the United States has gone down dramatically. Most use stopped several decades ago, but it is still used in some products.

Still, millions of Americans may already have been exposed to asbestos. People at risk for asbestos exposure in the workplace include some miners, factory workers, insulation manufacturers and installers, railroad and automotive workers, ship builders, gas mask manufacturers, plumbers, and construction workers. Family members of people exposed to asbestos at work can also be exposed because the workers can carry home asbestos fibers on their clothes.

Asbestos was also used to insulate many older homes, as well as commercial and public buildings around the country, including some schools. Because these particles are contained within the building materials, they are not likely to be found in the air in large numbers. The risk of exposure is likely to be very low unless the particles somehow escape into the air, such as when building materials begin to decompose over time, or during remodeling or removal.

The risk of developing mesothelioma is loosely related to how much asbestos a person is exposed to and how long this lasts. People exposed at an early age, for a long time, and at higher levels are more likely to develop this cancer. Still, most people exposed to asbestos, even in large amounts, do not get mesothelioma. Other factors, such as a person’s genes, may make them more likely to develop mesothelioma when exposed to asbestos.

Mesotheliomas related to asbestos exposure take a long time to develop. The time between first exposure to asbestos and diagnosis of mesothelioma is usually between 20 and 50 years. Unfortunately, the risk of mesothelioma does not go down over time after the exposure to asbestos stops. The risk appears to be lifelong.

For more detailed information on asbestos, see Asbestos and Cancer Risk.

Zeolites

Zeolites are minerals chemically related to asbestos. An example is erionite, which is common in the rocks and soil in parts of Turkey. High mesothelioma rates in these areas are believed to be caused by exposure to this mineral.

Radiation

There have been a few published reports of mesotheliomas that developed after people were exposed to high doses of radiation to the chest or abdomen as treatment for another cancer. Although the risk of mesothelioma is higher in patients who have been treated with radiation, this cancer is still rare in these patients.

There have also been reports linking mesothelioma to injections of thorium dioxide (Thorotrast). This radioactive material was used by doctors for certain x-ray tests until the 1950s. Thorotrast was found to cause cancers, so it has not been used for many decades.

SV40 virus

Some studies have raised the possibility that infection with simian virus 40 (SV40) might increase the risk of developing mesothelioma. Some injectable polio vaccines given between 1955 and 1963 were contaminated with SV40. As many as 30 million people in the United States may have been exposed to this virus.

Some lab studies have suggested that SV40 infection might cause mesothelioma. For example, infecting some lab animals like hamsters with SV40 causes mesotheliomas to develop. Researchers also have noticed that SV40 can cause mouse cells grown in lab dishes to become cancerous, and that asbestos increases the cancer-causing effect of SV40 on these cells. Other researchers have found SV40 DNA in some biopsy specimens of human mesotheliomas. But fragments of SV40 DNA can also be found in some non-cancerous human tissues.

So far, the largest studies looking at this issue in humans have not found an increased risk for mesothelioma or other cancers among people who received the contaminated vaccines as children. But the peak age range for diagnosis of mesothelioma is 50 to 70 years. Some researchers have pointed out that this issue may remain unresolved until more of the people accidentally exposed to SV40 between 1955 and 1963 reach that age range.

Most experts have concluded that at this time we still don’t know if SV40 is responsible for some mesotheliomas. This important topic is still being researched.

Age

The risk of mesothelioma increases with age. Mesothelioma can occur in young people (even children), but it is rare in people under age 45. About 2 out of 3 people with mesothelioma of the chest are 65 or older.

Gender

Mesothelioma is much more common in men than in women. This is probably because men have been more likely to work in jobs with heavy exposure to asbestos.

Researchers have found several factors that increase a person’s risk of mesothelioma, but it’s not yet clear exactly how all of these factors might cause this cancer.

Cancers, including mesotheliomas, occur when cells in the body suffer damage to their DNA. DNA is the chemical in each of our cells that makes up our genes – the instructions for how our cells function. We usually look like our parents because they are the source of our DNA. But DNA affects more than how we look. Some genes control when cells in the body grow, divide into new cells, and die at the right time. Changes in these genes may cause cells to grow out of control, which can lead to cancer.

Asbestos exposure is the main cause of pleural mesothelioma. When asbestos fibers are breathed in, they travel to the ends of small air passages and reach the pleura, where they can cause inflammation and scarring. This may damage cells’ DNA and cause changes that result in uncontrolled cell growth. If swallowed, these fibers can reach the abdominal lining, where they can have a role in causing peritoneal mesothelioma.

But most people exposed to asbestos, even in large amounts, do not get mesothelioma. Other factors, such as a person’s genes, may make them more likely to develop mesothelioma when exposed to asbestos. For example, researchers have found that some people who seem to be at high risk have changes in BAP1, a gene that normally helps keep cell growth under control. Other genes are probably important as well.

Radiation treatments for other cancers have been linked to mesothelioma in some studies. Radiation can damage the cells’ DNA, leading to out-of-control cell growth.

It is still not known if infection with the SV40 virus increases the risk of mesothelioma, or exactly how it might do so. In lab studies, researchers have found that the virus can affect certain genes that have been linked with cancer, but further research in this area is needed.

Being exposed to asbestos is by far the biggest risk factor for mesothelioma, so the best way to reduce your risk is to limit your exposure to asbestos at home, in public buildings, and at work.

People who might be exposed to high levels of asbestos at work include some miners, factory workers, insulation manufacturers and installers, railroad and automotive workers, ship builders, gas mask manufacturers, plumbers, and construction workers. If there is a chance of on-the-job exposure, such as during the renovation of old buildings, you should use all protective equipment and safety procedures designed for working around asbestos.

Older homes may have insulation containing asbestos or other materials. A knowledgeable expert can check your home to find out if there is any asbestos and whether it poses any risk of exposure. This may mean testing the air for asbestos levels. Just because asbestos exists in a home does not necessarily mean that it needs to be removed. As long as the material is not damaged or disturbed, for example by drilling or remodeling, the fibers will not be released into the air. If asbestos needs to be removed from your home, you should hire a qualified contractor to do this to avoid contaminating your home or causing any exposure to your family or to the workers. You should not attempt to remove asbestos-containing material yourself.

Asbestos can also be found in some commercial and public buildings (including some schools), where the same basic principles apply. Intact, undisturbed materials containing asbestos generally do not pose a health risk. They may pose a risk if they are damaged, are disturbed in some way, or deteriorate over time and release asbestos fibers into the air. By federal law, all schools are required to inspect materials with asbestos regularly and to have a plan in place for managing them.

For some people with mesothelioma, treatment may remove or destroy the cancer. Completing treatment can be both stressful and exciting. You may be relieved to finish treatment, but find it hard not to worry about the cancer coming back. (When cancer comes back after treatment, it is called recurrence.) This is a very common concern in people who have had cancer.

It may take a while before your fears lessen. But it may help to know that many cancer survivors have learned to live with this uncertainty and are leading full lives. See Understanding Cancer Recurrence for more about this.

For many people, the mesothelioma may never go away completely. These people may get regular treatments with chemotherapy, radiation therapy, or other therapies to help keep the cancer under control and help relieve symptoms from it. Learning to live with cancer that doesn’t go away can be difficult and very stressful. It has its own type of uncertainty. See Managing Cancer as a Chronic Illness talks more about this.

Follow-up care

If you have completed treatment, your doctors will still want to watch you closely. It’s very important to keep all follow-up appointments. During these visits, your doctors will ask about symptoms, examine you, and may order blood tests (such as the osteopontin or MesoMark tests) or imaging tests such as CT scans or PET scans. There is no widely agreed upon follow-up schedule for people with mesothelioma. Your doctor will most likely want to see you fairly often (at least every few months or so) at first. The time between visits may be extended if there are no problems.

Follow-up is needed to check for signs of cancer recurrence or spread, as well as possible side effects of certain treatments. This is a good time for you to ask your health care team any questions you might have and to discuss any concerns.

Almost any cancer treatment can have side effects. Some can last for weeks or months, but others can be permanent. Don’t hesitate to tell your cancer care team about any symptoms or side effects that bother you so they can help you manage them.

If the cancer does come back, further treatment will depend on where the cancer is, what treatments you’ve had before, and your health. For more on how recurrent cancer is treated, see Treatment of Mesothelioma Based on the Extent of the Cancer. For more general information on dealing with a recurrence, see Coping With Cancer Recurrence.

Seeing a new doctor

At some point after your treatment, you may be seeing a new doctor who doesn’t know anything about your medical history. It’s important to be able to give your new doctor the details of your diagnosis and treatment. Gathering these details soon after treatment may be easier than trying to get them at some point in the future. Make sure you have the following information handy (and always keep copies for yourself):

• A copy of your pathology report(s) from any biopsies or surgeries
• Copies of imaging tests (such as x-rays or CT or MRI scans), which can usually be stored digitally (on a DVD, etc.)
• If you had surgery, a copy of your operative report(s)
• If you stayed in the hospital, a copy of the discharge summary that the doctor wrote when you were sent home
• If you had radiation therapy, a summary of the type and dose of radiation and when and where it was given
• If you had chemotherapy, a list of your drugs, drug doses, and when you took them
• The names and contact information of the doctors who treated your cancer

It’s also very important to keep health insurance. Tests and doctor visits cost a lot, and even though no one wants to think of their cancer coming back, this could happen. For more information, see Understanding Health Insurance.