Pleural mesothelioma is a form of cancer that develops in the pleura, which is the membrane between the lungs and the chest wall.
It’s estimated that 3,000 people, mostly men over the age of 70, are diagnosed with malignant mesothelioma each year. Of those, approximately 80% are diagnosed with malignant pleural mesothelioma (MPM).
Symptoms include chest pain, breathing issues, and a dry cough. Without proper mesothelioma treatment, pleural mesothelioma patients usually live for only six to nine months, but treatments can help to extend this.
What is pleural mesothelioma?
Malignant pleural mesothelioma (MPM) is the most common form of mesothelioma cancer that forms in the lining surrounding specific organs. It is a relatively rare yet aggressive form of cancer, which accounts for less than 0.3% of all cancer diagnoses in the U.S. and has a 5-year survival rate of less than 5%.
Pleural mesothelioma is the most common type of mesothelioma, followed by peritoneal mesothelioma (which forms in the abdomen) and pericardial mesothelioma (near the heart).
Most cases of pleural mesothelioma are caused by inhaling asbestos fibers into the lungs. Asbestos refers to a group of silicate minerals found regularly in the insulation of older buildings, like churches, hospitals, homes, military ships, and auto parts.
After exposure, asbestos embeds itself into the lining of the lungs, causing inflammation and scarring over time. As scarring intensifies over several decades, it can eventually develop into mesothelioma tumors. Asbestos exposure is the only known risk factor for mesothelioma.
Asbestos exposure does not cause mesothelioma right away. It usually takes 20 to 40 years, and sometimes even longer, for someone to develop mesothelioma after asbestos exposure. This time is called the latency period. This can make it difficult for those exposed during childhood or early adulthood to connect their current symptoms and long-forgotten exposure.
What Are The Symptoms of Pleural Mesothelioma?
Many of the symptoms of pleural mesothelioma are related to the lungs and other parts of the respiratory system. Some of the respiratory symptoms include:
- Cough, which is usually dry and often painful
- Pain in the chest or back
- Shortness of breath, or the feeling that you can’t expand your chest enough to get enough air
- Trouble swallowing
- Hoarseness of the voice, which lasts longer than a few days
In addition to the respiratory symptoms, MPM patients may experience some or all of these general symptoms:
- Fever
- Night sweats
- Fatigue
- Unexplained weight loss
- Blood clots
- Loss of appetite
Many of the symptoms of pleural mesothelioma can also be caused by other diseases, many of which are more common than mesothelioma. MPM may be misdiagnosed as one of these conditions. Some of them include:
- Lung infections (such as pneumonia or influenza)
- COPD (lung damage caused by chronic irritation, usually from smoking)
- Asthma
- Other types of cancer (such as lung cancer)
What Causes Pleural Mesothelioma?
The primary risk factor for malignant pleural mesothelioma is occupational or environmental asbestos exposure. Between 70% and 80% of mesothelioma cases involve significant asbestos exposure.
Worldwide, there has been a significant uptick in diagnoses in countries that have undergone heavy industrialization in recent decades, especially in places that have neither regulated nor banned the use of asbestos. In the U.S., the use of asbestos is heavily regulated, but many people are surprised to learn that it’s still not completely banned.
Occupations that are most at risk for asbestos exposure and, therefore, pleural mesothelioma include:
- Firefighters
- Military veterans
- Construction workers
- Industrial workers
- Power plant workers
- Shipyard Workers
- Metalworkers
The families of people who worked in these industries may also be at risk because they can be exposed to asbestos brought home on a worker’s clothing, skin, and hair.
How Is Pleural Mesothelioma Diagnosed?
Diagnosing pleural mesothelioma can be somewhat tricky for a few reasons. One is that the disease symptoms are similar to the symptoms of many other diseases, many more common than mesothelioma. Another is the long period between asbestos exposure and the development of mesothelioma.
Typically, the first step in diagnosis is a chest X-ray. This may reveal one or more tumors in the lungs. A mesothelioma tumor may be tiny and may only be visible as an area of pleural thickening on the X-ray. The X-ray might also show a pleural effusion, which is fluid buildup around the lungs.
These findings on the X-ray strongly suggest some type of malignancy, but they don’t show its type. More testing will be needed to get a definitive mesothelioma diagnosis. This may include:
- Additional imaging: A CT scan of the chest may be used. This is a more detailed scan than an X-ray. Other imaging studies, like an MRI or PET scan, are sometimes also helpful.
- A biopsy: This is a small sample of the tissue, which can be examined in the laboratory to see what type of tumor cells are present. The biopsy is most commonly obtained during a surgical procedure called thoracoscopy. The surgeon makes a small incision in the chest wall and inserts a flexible plastic tube with a light and a camera on the end. This allows the surgeon to get the tissue sample for the biopsy, look around and check for tumors in the chest cavity, and drain any pleural fluid accumulated.
- Blood tests: In some cases, a set of blood tests called immunochemistry is used. This looks for particular proteins in the blood. It can help to distinguish different types of cancer from each other to confirm the diagnosis.
Pleural mesothelioma cell types
The cell type of cancer can be classified as pleural mesothelioma. There are three types of mesothelioma:
- Epithelioid mesothelioma: This type spreads the most easily but tends to be more treatable. This is the cell type with the best prognosis.
- Sarcomatoid mesothelioma: This type is the most difficult to treat, although it also may spread more slowly.
- Biphasic mesothelioma: This type has characteristics in between the other two types.
The biopsy will show which cell type a patient has. This will play a role in determining the appropriate mesothelioma treatment plan for that patient.
Stages of pleural mesothelioma
The stage of cancer refers to how far the cancer has spread within the body. For pleural mesothelioma, the most widely used system is called the TNM staging system. This system uses three characteristics to determine the stage of the cancer:
- T – Tumor: What is the size of the original tumor, and has it spread to nearby areas (such as into the chest wall)?
- N – Node: Have the cancer cells spread to nearby lymph nodes?
- M – Metastasis: To what degree has the cancer spread to areas that are distant from the original tumor?
A number after each letter shows how far the cancer has advanced (for example, T3 N1 M0). To determine each of these characteristics accurately, doctors use imaging tests (such as a CT scan or PET scan) as well as biopsy results. To determine lymph node involvement, biopsies of lymph nodes can be taken during a thoracoscopy procedure.
How is Pleural Mesothelioma Treated?
In most cases, malignant pleural mesothelioma is treated using a combination of different treatments. It’s often best to be treated at a cancer center, where a mesothelioma specialist can help to create the best mesothelioma treatment plan for this rare cancer.
- Surgery: In cases where a cure is more likely to be possible (an epithelioid tumor found at an early stage), a very invasive procedure called extrapleural pneumonectomy may be used. This procedure removes the lung and many other tissues on the affected side. Less invasive procedures, such as pleurectomy/decortication, may also be used.
- Chemotherapy: The chemotherapy drugs may be given into the bloodstream through an IV, where they will affect the whole body. They may also be placed directly into the chest cavity during a surgical procedure; this is called intrathoracic chemotherapy. Chemotherapy can be used before or after surgery, or it can be given to patients who are not candidates for surgery.
- Radiation therapy: Technology allows for multiple weaker beams of radiation to be aimed at the tumor from different directions. At the site of the cancer, all of the beams cross. This gives a high dose of radiation to the cancer cells while causing less damage to the surrounding tissue. Radiation is often used after surgery, to help decrease the chance that the tumor will grow back. It can also be used for palliative care, to help shrink a tumor that is causing symptoms.
- Immunotherapy: This form of treatment stimulates the patient’s immune system, causing it to destroy cancer cells. This has been in clinical trials for many years, but two forms of immunotherapy are now FDA-approved for the treatment of malignant pleural mesothelioma.
What Are the Emerging Treatments for Pleural Mesothelioma?
In addition to the currently approved treatment options, there are also a variety of new treatments that are currently being studied for pleural mesothelioma.
Although the research is not yet complete, some of these experimental treatments are showing promising results and could become more widely available to patients in the future. Many are also being used successfully for patients with other types of cancer. Some treatments that are currently in clinical trials include:
- Immunotherapy: Although the FDA has approved two immunotherapy treatments for certain patients with malignant pleural mesothelioma, this form of therapy is still being improved. There are clinical trials currently underway to test new immunotherapy treatments for MPM.
- Photodynamic therapy: This form of treatment uses a photosynthesizer (a drug) which is activated by light to destroy malignant cells. PDT can only be used along with surgery since the cancer cells must be exposed to light to activate the drug.
- Gene therapy: This form of treatment involves adding genes to the existing cancer cells to make them easier to kill. The new genes may be delivered via modified viruses, which can infect cancer cells and change them genetically.
- Treatment combinations: For example, new combinations of chemotherapy drugs, surgery, and radiation therapy are being tested to determine the most effective combinations and the ideal timing for the various treatments.
- Complementary medicine: A variety of alternative medical treatments, including medical marijuana, acupuncture, and dietary supplements, may help with symptom relief and might help to keep patients more comfortable as they complete their treatments.
If you’re interested in trying one of these experimental treatments, the only way to get access is to participate in a clinical trial. There are both benefits and risks to being part of a trial. We recommend that you discuss this option with your doctor to help you decide whether it’s right for you.
There may be very specific requirements for participating in a particular trial (such as the cancer being in a certain stage), so you won’t be eligible for all of them. The National Cancer Institute (NCI) maintains a database of trials for mesothelioma, which you can use to look for trials that you would be eligible for. Your doctor can help you to determine which trials might be options for you.
What’s The Typical Pleural Mesothelioma Prognosis?
As with any diagnosis, each person’s medical journey will be unique. In general, pleural mesothelioma tends to progress relatively quickly. Unfortunately, the prognosis is poor for many patients, with a median survival of 18.4 months. Several factors can affect the prognosis of a person.
- Age: The median survival rate is longer for younger people. 18-44-year-olds have a median survival of 59 months, while for those 75 or older, it’s only 10 months.
- Sex: The survival rate is higher for women than men, perhaps in part due to higher levels of estrogen.
- Stage: Those who are diagnosed at an earlier stage have a better overall survival rate, with a median time of 21 months for stage I cases, compared with 12 months for stage IV cases.
- Histology: Cases with epithelioid cells (rather than biphasic or sarcomatoid cells) have a better survival rate.
- Treatment: Receiving appropriate treatment can help to extend survival for many patients. Which treatments are beneficial depends on the patient’s specific situation.
For untreated cases, the median survival rate is between six and nine months. With the proper treatment plan, however, many patients live much longer. Despite the relatively poor overall prognosis for pleural mesothelioma, advancements in the field have led to increased optimism.
