What is mesothelioma?
Mesothelioma is cancer affecting mesothelial cells. These cells form a moist (serous) layer that covers internal organs and lines body cavities, such as the chest and abdomen. This layer is the mesothelium. It produces a fluid that reduces friction between organs and structures as they move inside the body. With this lubrication, organs can slide against other organs and structures, which protects them from damage. The mesothelium goes by different names in different parts of the body.
The most common mesothelioma affects the layer covering the lungs and chest cavity. This layer is called the pleura. Up to 80% of mesotheliomas develop in the pleura. The next most common body site is the layer that lines the abdomen—the peritoneum. About 10 to 20% of mesotheliomas begin in the peritoneum. The other two main types of mesothelioma are very rare and affect the pericardium—layer around the heart—and the tunica vaginalis— a membrane that surrounds a man’s testicles.
There are three types of mesothelioma. The names for them reflect the way the cells look:
Epithelioid: The cells resemble epithelial cells, which normally make up the mesothelium. About 70% of mesotheliomas are epithelioid. This type usually has the best prognosis because it often grows slowly and responds better than other types to chemotherapy.
Sarcomatoid: The cells are fibrous. This type accounts for 10 to 20% of mesothelioma cases. It is more resistant to treatment and usually does not respond to chemotherapy as well as the other types.
Mixed or biphasic: Cells of both types are present. It makes up the remaining cases of mesothelioma. It falls in the middle as far as response to chemotherapy.
In the United States, mesothelioma is a relatively rare cancer. There are about 3,000 new cases each year, mostly in men. Exposure to asbestos, usually in the workplace, is the main risk factor for most cases of mesothelioma. This may explain why more men than women get this cancer. Over the last 30 years, the rate of mesothelioma has leveled off, mainly due to changes in workplace exposures.
Mesothelioma symptoms start off vague and are usually minor. As the cancer progresses, symptoms become more noticeable. For pleural mesothelioma, this may include chest pain, cough, and shortness of breath.
Mesothelioma can be difficult to treat. It doesn’t grow as a single tumor mass the way many cancers do. Instead, the tumor grows and spreads along the mesothelium layer. This means surgery and radiation are usually not useful. Chemotherapy is the main treatment for mesothelioma. Targeted therapy and immunotherapy may also be options.
Finding and treating mesothelioma as early as possible offers the best chance of beating the disease. Seek prompt medical care if you have a cough or shortness of breath that persists for more than a few days or worsens over time. Seek immediate medical care (call 911) if you have chest pain or trouble breathing.
What are the symptoms of mesothelioma?
Symptoms can be easy to overlook in the early stages of mesothelioma. They are often minor and vague. People may not realize something is wrong until the cancer has grown and spread. The symptoms mesothelioma depend on the area the cancer affects. Fatigue, fever, night sweats, loss of appetite, and unintended weight loss are common to all mesotheliomas.
Common symptoms pleural mesothelioma are:
Chest pain or lower back pain, which may get worse with deep breathing
Cough, which may be painful
Fluid buildup in the chest (pleural effusion)
Common symptoms of peritoneal mesothelioma are:
Constipation or bowel blockage
Fluid buildup and swelling in the abdomen (ascites)
Several more common conditions share these same symptoms. Due to the rarity of mesothelioma, the cause is more likely to be something else. However, it is important to see your doctor when any of these symptoms persist. They can be red flags for other serious and potentially life-threatening conditions. Regardless of the cause, seeking a prompt diagnosis may result in a better outcome.
What causes mesothelioma?
Doctors know certain factors increase the risk of getting mesothelioma. However, they don’t fully understand exactly how it, or any other cancer, occurs or how those factors lead to cancer. Cancer happens when something damages a cell’s DNA. The damage somehow causes healthy cells to lose control of their own growth and reproduction. This out of control cell growth is the root of cancer. That’s why powerful chemotherapy drugs that kill rapidly dividing cells are one of the primary methods of controlling mesothelioma.
What are the risk factors for mesothelioma?
Asbestos exposure is responsible for up to 80% of mesothelioma cases. It is possible to breathe in or swallow asbestos fibers. When the fibers reach the lining of the lungs or abdomen, they can cause inflammation and scarring. This likely contributes to the DNA damage that leads to cancer.
Asbestos was a common component of building materials until the 1990s. This included insulation, ceiling tiles, and roof shingles. It was useful because it was resistant to fire. But health concerns eventually phased out its use. Newer building materials do not contain asbestos. However, older buildings can still have asbestos materials. This does not pose a risk as long as the material remains undisturbed. If an older building needs renovating, workers removing these materials must wear protective gear to prevent exposure to asbestos.
Other risk factors for mesothelioma include:
Age 65 or older
Family history of mesothelioma, which may be related to the BAP1 gene mutation
Living with someone who works with asbestos, as asbestos fibers can come home on clothing and other personal items
Male gender, which may be related to work exposure to asbestos
Radiation therapy to the chest or abdomen
Reducing your risk of mesothelioma
Cancer risk reduction involves changing the risk factors you can control. Avoiding asbestos exposure greatly reduces your risk due to the strong relationship between asbestos exposure and mesothelioma. Occupations at risk for asbestos exposure include mining, construction, plumbing, factory work, railroad work, ship building, and automotive work. To protect yourself in any of these settings, wear protective gear. To avoid carrying fibers home, shower and change before leaving work.
You may also be at risk if you are remodeling an older home. Never attempt to remove or disturb asbestos-containing materials yourself. Contact an asbestos removal company to accomplish the job safely.
How is mesothelioma treated?
After a mesothelioma diagnosis, doctor’s need to determine the stage, or extent of the cancer. This helps guide treatment. Mesothelioma treatment options include:
Chemotherapy, which is the main treatment for mesothelioma. Doctors can give it through a vein or infuse it directly into the chest or abdominal cavity. Chemotherapy can slow mesothelioma, but it is unlikely to cure it.
Immunotherapy, which is an option for cancers still growing after chemotherapy. Immunotherapy is a type of targeted therapy that stimulates the immune system to fight cancer. Currently, there are three drugs for mesothelioma: pembrolizumab (Keytruda), nivolumab (Opdivo), and ipilimumab (Yervoy).
Targeted therapy, which can work when standard chemotherapy does not. Targeted therapy targets genes and proteins to slow cancer growth. Currently, doctors use drugs that target a protein necessary to form new blood vessels. The drug bevacizumab (Avastin) in combination with chemotherapy drugs can help people with mesothelioma live longer.
Surgery, which removes the pleura and as much of the cancer as possible. Doctors use this surgery in some cases, when the chance of a cure is high. Unfortunately, it’s common for some cancer cells to remain, causing the cancer to return.
Radiation therapy, which is challenging in treating mesothelioma due to the way the cancer grows. It’s difficult to deliver radiation to kill mesothelioma cells without damaging the lungs. Doctors most often use it after extensive surgery to remove both the pleura and the lung. It can also help relieve cancer symptoms in advanced cases.
What are the potential complications of mesothelioma?
Mesothelioma is typically difficult to treat. By the time people find out they have it, mesothelioma is often advanced. As a result, the survival rate is not high.
Factors that can influence survival include the type of mesothelioma and its extent. People tend to live longer when the extent is limited and surgery can remove all or most of the cancer. Age also plays a role, with younger people typically surviving longer. Other things can play a role, such as your overall health and the cancer’s responsiveness to treatment. Your doctor is best able to help you understand how these factors affect your outlook.