Mesothelioma Malignant

Malignant mesothelioma is a rare and aggressive cancer that develops in the thin layer of tissue covering internal organs, most commonly the lungs. This disease is strongly linked to asbestos exposure and can take decades to appear after contact with this harmful mineral.

Table of contents

• What is malignant mesothelioma?
• Types of mesothelioma
• What causes mesothelioma?
• Signs and symptoms
• How is mesothelioma diagnosed?
• Treatment options
• Prognosis and survival
• Prevention

What is malignant mesothelioma?

Mesothelioma is a cancer that starts as a growth of cells in the mesothelium, which is a thin layer of tissue that covers many internal organs^[1]. The mesothelium is like a protective wrapping that surrounds and protects organs such as the lungs, the organs in your belly, your heart, and testicles^[2]. This tissue normally produces a special fluid that allows organs to move smoothly against each other when you breathe or move^[8].

Mesothelioma is sometimes called malignant mesothelioma because it is a fast-growing and deadly form of cancer^[1]. Unlike many other types of cancer, mesothelioma often does not grow as a single tumor. Instead, it can spread along the thin tissue, and over time may form multiple tumors that sometimes combine into a sheet covering the affected organs, making it harder to treat^[2].

This is a rare disease, with approximately 3,000 new cases diagnosed each year in the United States^[6]. Most people who develop mesothelioma are over 65 years old, and men are much more likely than women to get this disease^[8].

Types of mesothelioma

Mesothelioma can develop in different parts of the body, depending on which area of the mesothelium is affected. The most common type affects the tissue around the lungs^[1].

Pleural mesothelioma affects the tissue around the lungs, called the pleura. This is the most common form, accounting for about 80% of all mesothelioma cases^[12]. The pleura is like a cellophane wrap around the chest wall and lung^[6]. When mesothelioma develops there, this wrapping becomes thickened with tumor, almost like a blanket^[6].

Peritoneal mesothelioma affects tissue in the belly, called the peritoneum. This is the second most common type of mesothelioma, representing 10 to 20 percent of cases^[8]. The peritoneum is a thin membrane that lines the abdominal cavity and the surface of the abdominal organs^[9].

Pericardial mesothelioma affects tissue around the heart, called the pericardium. This type is extremely rare^[2]. It may cause trouble breathing and chest pains^[1].

Mesothelioma of the tunica vaginalis affects tissue around the testicles. This is also extremely rare^[2]. It may first appear as swelling or a mass on a testicle^[1].

Mesothelioma can also be classified by the types of cells involved. There are three main cell types: epithelioid mesothelioma is the most common and tends to have a better outlook; sarcomatoid mesothelioma accounts for about 10% of cases and is harder to treat; and biphasic mesothelioma contains a mix of both cell types and represents 30 to 40 percent of cases^[9]. The type of cells present can affect treatment options and prognosis^[12].

• Pleura (tissue covering lungs)
• Peritoneum (tissue lining abdomen)
• Pericardium (tissue surrounding heart)
• Tunica vaginalis (tissue around testicles)

What causes mesothelioma?

Exposure to asbestos is the most common cause of mesothelioma, accounting for 70% of cases^[12]. Asbestos is a group of minerals naturally found in rocks and soil that form long, thin, very strong fibers^[3]. These fibers do not evaporate or dissolve in water, and they resist heat and fire^[3].

Asbestos was used in many consumer products, automobile parts, and building materials during the 20th century, before scientists learned about its dangers to health^[3]. When asbestos-containing materials are disturbed, they can release tiny fibers into the air that are too small to see. If you breathe in or swallow these fibers, they can settle in your lungs or abdomen. They are too tough for your body to break down, and over time they can cause scarring, inflammation, and cell changes that lead to cancer^[12].

The time between first exposure to asbestos and developing mesothelioma is usually between 20 and 50 years^[8]. This long delay means that many people diagnosed with mesothelioma today were exposed to asbestos decades ago, possibly before safety regulations were put in place.

Not everyone who is exposed to asbestos will develop mesothelioma^[3]. In fact, only about 5% of people in high-risk populations develop this cancer^[15]. And some people with mesothelioma do not have a known history of asbestos exposure^[2].

Other risk factors for mesothelioma include^[2][4]:

• Having a job that exposed you to asbestos, such as construction, shipbuilding, mining, military service, or auto repair
• Living with someone who works with asbestos, as fibers can be carried home on clothing
• Radiation exposure, including radiation treatments to the chest for a previous cancer
• Exposure to erionite, an asbestos-like mineral once used in road construction
• Genetics, particularly inherited changes in the BAP1 gene
• Being male, as more males than females develop mesothelioma

It is important to note that smoking itself does not contribute to mesothelioma^[4]. However, the combination of smoking and asbestos exposure significantly increases the risk of lung cancer.

Signs and symptoms

The symptoms of mesothelioma depend on where the cancer is located in the body. Symptoms often develop slowly and may not appear until decades after asbestos exposure^[1]. Early signs can be bothersome but easy to dismiss, which is why many people delay seeing their healthcare provider until their cancer is more advanced^[12].

Pleural mesothelioma, which affects the tissue around the lungs, may cause^[1][2]:

• Chest pain, especially under the rib cage
• Painful coughing
• Shortness of breath that gets worse over time
• Lumps under the skin on the chest
• Tiredness
• Weight loss without trying
• Difficulty swallowing
• Hoarseness

Peritoneal mesothelioma, which affects tissue in the belly, may cause^[1][2]:

• Belly pain
• Belly swelling
• Nausea
• Tiredness
• Weight loss without trying
• Diarrhea
• Loss of appetite
• Vomiting

Other symptoms that can occur with any type of mesothelioma include fever, night sweats, and swelling or lumps in various parts of the body^[2].

Sometimes the cancer causes fluid to collect in the chest or abdomen, which can contribute to symptoms^[5]. If you have any of these symptoms, it is important to talk to your doctor. They may be caused by something other than cancer, and the only way to know what is causing them is to see your doctor^[3].

How is mesothelioma diagnosed?

Diagnosing mesothelioma can be challenging because it is rare and shares symptoms with more common illnesses like the flu, pneumonia, or digestive problems. It is sometimes mistaken for these other conditions^[21]. The time to confirm a diagnosis varies, making the process difficult^[14].

If you have symptoms that suggest mesothelioma, your doctor will need to find out if they are caused by cancer or another problem^[5]. The doctor will ask when the symptoms started and how often you have them. A physical exam may be done to check for lumps or other signs^[11].

Several tests are used to look for mesothelioma and examine the inside of the chest and abdomen^[1][3]:

• Imaging tests such as chest x-rays, CT scans, MRI scans, or PET scans to create pictures of the inside of your body
• Blood tests to look for certain markers
• Procedures to remove fluid or tissue samples for testing

A biopsy is the only way to confirm or rule out mesothelioma^[11]. During a biopsy, a doctor removes a sample of tissue for testing in a laboratory. The type of biopsy depends on what area of the body is affected. The doctor might remove fluid or tissue with a thin needle inserted through the skin, or a surgeon might take a sample during surgery by making a small cut and inserting a tube with a video camera to see inside the chest or belly^[11].

The tissue sample is examined in a lab to determine if it is mesothelioma and, if so, what type of cells are involved^[11]. Once mesothelioma is confirmed, additional tests may be done to find out if the cancer has spread to lymph nodes or other areas of the body. These results help determine the stage of the cancer, which guides treatment decisions^[11].

Treatment options

Treatment for mesothelioma depends on where the cancer is located, whether it has spread, the type of cancer cells present, your general health and fitness level, and your personal wishes^[19]. A team of doctors and other professionals, called a multidisciplinary team, will discuss the best treatment and care for you^[19].

Unfortunately, mesothelioma can be difficult to treat. It is often diagnosed at an advanced stage, so nearly all treatments aim to control the cancer for as long as possible and keep symptoms under control^[19]. For many people with mesothelioma, there is no cure^[1]. However, treatments can help people live longer and maintain quality of life.

The main treatment options include^[3][5]:

Surgery is an operation in which doctors cut out the cancer. Not everyone is a candidate for surgery. You must be fairly fit and well to undergo and recover from the procedure^[19]. For early stage mesothelioma, surgeons may remove part of the pleura, the whole pleura, or perform more extensive surgery to remove as much cancer as possible^[19]. Surgery can help control symptoms and may help some patients live longer.

Chemotherapy uses special medicines to shrink or kill cancer cells. The drugs can be pills you take or medicines given through your veins, or sometimes both^[3]. Common chemotherapy drugs for mesothelioma include pemetrexed in combination with cisplatin or carboplatin^[16][19]. Chemotherapy can be given before surgery, after surgery, or to shrink and control advanced cancer.

Radiation therapy uses high-energy rays, similar to x-rays, to kill cancer cells^[3]. It may be used after surgery for early stage mesothelioma or to control symptoms and slow down cancer growth^[19].

Immunotherapy uses special medicines to help your body’s immune system fight the cancer^[3]. In 2020, the combination of nivolumab and ipilimumab was approved for first-line treatment of unresectable mesothelioma, showing significant improvements in survival compared to standard chemotherapy^[16]. Immunotherapy is used for patients who cannot have surgery and must be fit enough to tolerate treatment^[19].

Targeted therapy uses drugs to block the growth and spread of cancer cells. The drugs can be pills or medicines given through your veins. You will get tests to see if targeted therapy is right for your cancer type before this treatment is used^[3].

Often, a combination of treatments, called multimodal therapy, gives patients better chances of survival^[13]. For instance, patients might have surgery followed by chemotherapy and radiation. More aggressive cancer treatments can improve outcomes for eligible patients^[24].

Palliative care focuses on relieving symptoms and improving quality of life^[19]. This is especially important for people with advanced mesothelioma who may be too ill to cope with intensive treatments. Palliative treatments can control symptoms such as pain, breathing problems, and fluid buildup. A team of doctors and nurses who are experts in controlling symptoms manages this care^[19].

Clinical trials offer access to new treatment options that are being tested^[3]. Your doctor might ask if you would like to take part in a clinical trial, which can provide hope for better treatments in the future.

Prognosis and survival

Mesothelioma is usually a terminal diagnosis, meaning that most patients will not be cured^[24]. The prognosis, or likely outcome, depends on several important factors including the stage of the cancer, your age, performance status, and the type of cells involved^[14].

The average life expectancy for mesothelioma is about 12 to 21 months after diagnosis^[26], with many sources citing an average survival time of about one year^[8]. However, the five-year survival rate is approximately 12%^[15], meaning that some patients do live much longer.

Several factors affect prognosis^[14]:

• Stage of the cancer: Earlier stages have better outcomes
• Age: Younger patients tend to do better
• Performance status: People who are more active and able to care for themselves have better outcomes
• Cell type: Epithelioid mesothelioma generally has a better prognosis than sarcomatoid types
• Whether the cancer can be surgically removed

An early diagnosis is one of the most important factors in patients who survive longer with mesothelioma^[24]. Catching the cancer early allows patients to benefit from more aggressive and effective treatments. Starting treatment as soon as possible helps slow tumor growth, prevents tumors from spreading, and in some cases may eliminate tumors entirely^[24].

While these statistics show the challenges of mesothelioma, there are survivors who have lived for many years after diagnosis. Some patients have survived for 25 years or more^[26]. These long-term survivors often had early diagnosis, aggressive multimodal treatment, and worked with experienced mesothelioma specialists.

Prevention

There is no sure way to prevent mesothelioma, but it is important to stay away from or limit exposure to asbestos^[8]. This is especially important for people who work in certain industries such as construction, shipbuilding, insulation manufacturing, textile manufacturing, mining, military service, and auto repair^[2][4].

If you work in an environment where asbestos may be present, follow all safety precautions. You may need to wear protective clothing and a respirator^[8]. Employers in these industries should provide proper safety equipment and training.

Many older homes and buildings may contain materials made with asbestos. If you think asbestos may be in your home, ask an expert to check it^[8]. Intact materials containing asbestos are safe; asbestos only poses a health risk when disturbing the material releases fibers into the air^[12]. Do not disturb asbestos or try to remove it yourself. If removal is needed, hire a trained asbestos expert^[8].

Living with a person who works near asbestos is also a risk factor, as asbestos fibers can be carried home on clothing^[5][8]. Family members of workers exposed to asbestos have an increased risk of mesothelioma because of this secondary exposure.

If you have been exposed to asbestos in the past, talk to your doctor about regular cancer screenings and watch carefully for symptoms^[24]. Speak up about any persistent symptoms you may have, especially if doctors have not clearly identified a diagnosis. The earlier you receive a diagnosis, the better the chances of survival^[24].

Asbestos is no longer mined in the United States, but it is still imported from other countries to make some products, and it is still present in some older homes and buildings^[3]. The implementation of rigorous regulations in developed countries during recent decades has reduced exposure and is expected to eventually decrease the incidence of this disease^[15].