Mesothelioma is cancer in the membrane of various organs. Pleural mesothelioma, also called malignant pleural mesothelioma or MPM, is found in the membrane between the lungs and chest wall, called the pleura. Asbestos is the only known risk factor for this cancer. Without treatment, the average life expectancy of pleural mesothelioma is six months following diagnosis. Surgery, chemotherapy, radiation therapy, and other treatments can extend life expectancy by a limited amount.
Pleural mesothelioma, also known as malignant pleural mesothelioma or MPM, is a relatively rare and aggressive type of cancer. It forms in a membrane called the pleura, which is located between the lungs and the chest wall. Asbestos exposure is the only known risk factor for this disease. Life expectancy after diagnosis is generally less than two years, and long-term survival is uncommon, although the medical community hopes that emerging treatments will lead to better outcomes.
Pleural Mesothelioma Risk Factors
The only known risk factor for malignant pleural mesothelioma is exposure to asbestos. This is a mineral that was commonly used for many years in various industrial and military applications because it’s extremely stable and highly heat-resistant. More than 80% of mesothelioma patients have a known history of asbestos exposure.
When a person inhales small particles of asbestos, these become embedded in the lungs. The tiny particles can then migrate through the lung tissue into the surrounding pleura. A strong inflammatory response is triggered by the presence of asbestos. Because asbestos is too stable to be broken down, this response is sustained for years.
Over time, this inflammation can cause scarring in the lungs, which is known as asbestosis. It can also cause damage to the DNA of cells, which may eventually lead to cancer. It can take 20 to 40 years or longer for mesothelioma to develop. While asbestos exposure is most strongly associated with the development of mesothelioma, it also increases the risk of other types of cancer, including lung cancer, which forms in the lung tissue itself rather than in the pleura around the lungs.
People who worked in certain industries where asbestos use was historically common are at the greatest risk for malignant pleural mesothelioma. Unfortunately, companies did not always choose to provide their workers with adequate protection, even after the dangers of asbestos were known. Some of those at high risk include:
In addition, the families of workers may also be at risk. Asbestos fibers can travel on a worker’s clothes, skin, and hair to enter the home and be inhaled by family members.
The use of asbestos is now heavily regulated in the United States, and the incidence of malignant pleural mesothelioma has declined. However, some people are surprised to learn that asbestos is not completely banned in the United States, and asbestos imports are still occurring.
Malignant Pleural Mesothelioma Symptoms
People with pleural mesothelioma cancer may experience a variety of symptoms, including:
Pleural Mesothelioma Diagnosis
When a patient first visits their doctor with symptoms, the doctor will consider many different possible causes. Often, one of the first steps in the diagnosis is a chest X-ray. If the patient has pleural mesothelioma, this may show the tumor, or it may show an area of pleural thickening or a pleural effusion—fluid buildup around the lungs. However, the specific type of tumor won’t be evident from the X-ray.
Additional imaging studies, such as a computerized tomography (CT) scan, are often used next. A CT scan is more detailed than an X-ray and can show the precise location of the tumor. In some cases, other imaging studies, such as an MRI or a PET scan, are also performed to locate the cancer and determine how far it has spread.
The definitive diagnosis of pleural mesothelioma can be established only by a biopsy, which involves taking out a small piece of the tumor. The sample is sent to a pathologist, who looks at the cells under a microscope and tests them to determine whether they’re cancer cells and, if so, what type.
For patients with malignant pleural mesothelioma, there are a few different ways to obtain a biopsy sample.
Blood tests known as immunochemistry are sometimes used to confirm the diagnosis. These tests look for particular proteins in the blood in order to distinguish different types of cancer from each other.
Pleural Mesothelioma Cell Types
The histology or cell type of mesothelioma is an important prognostic factor and makes a significant difference in a patient’s treatment options. The three cell types are:
Malignant Pleural Mesothelioma Stages
The stage of a cancer refers to how advanced the disease is and is reported as a number from one to four. For malignant pleural mesothelioma, there’s an official system, called the TNM staging system, for determining the stage.
Unfortunately, many cases of pleural mesothelioma are diagnosed in their later stages. This is because the cancer is fairly aggressive, and the diagnosis is challenging.
Pleural Mesothelioma Life Expectancy
Long-term remission from malignant pleural mesothelioma is unfortunately rare, and malignant pleural mesothelioma is generally considered to be an incurable cancer. Treatments may extend a person’s life but are unlikely to eliminate the cancer entirely. It’s hoped that new treatments will lead to a better prognosis.
Malignant pleural mesothelioma life expectancy is not high for most patients. Without any treatment, a pleural mesothelioma patient can be expected to live an average of six months following diagnosis.
Treatment can extend this time, but life expectancy is limited. Studies have shown median survival rates of about 15 to 22 months, depending on the stage of the cancer at the time of diagnosis. Only 12% of malignant pleural mesothelioma cancer patients survive for five years.
Treatment of Pleural Mesothelioma
The treatment plan for a malignant pleural mesothelioma patient depends on factors including stage and cell type. Most patients receive multimodality therapy, which means using multiple types of treatments.
The management of malignant pleural mesothelioma often involves specialists in various fields, including medical oncology, thoracic surgery and radiation oncology. Many pleural mesothelioma patients are treated at a cancer center to have access to all of the care that they need.
In early stages, doctors may use aggressive treatment to try to eliminate the cancer. In later stages, treatment is often focused on palliative care, which is aimed at improving quality of life rather than longevity.
Surgery for Pleural Mesothelioma
This is a slightly less invasive procedure. The surgeon removes the pleura on the affected side, along with any apparent tumors. Pleurectomy/decortication carries a lower risk than extrapleural pneumonectomy, and some studies have shown that it’s equally effective at improving patient survival, although more research is needed.
Pleurodesis, which is a procedure that attaches the two layers of the pleura to prevent fluid buildup, may help those who experience repeated pleural effusions.
Many pleural mesothelioma cancer patients receive chemotherapy through an IV. This method delivers the medication to the whole body, which can help to destroy any cancer cells that have migrated away from the original tumor. In most cases, chemotherapy involves a combination of pemetrexed with either cisplatin or carboplatin. Studies have shown that chemotherapy can significantly improve survival, though it does cause significant side effects.
Another method is called heated intrathoracic chemotherapy. This method is similar to the Sugarbaker treatment, which has been successfully used for peritoneal mesothelioma—found in the abdomen—for years.
The thoracic surgeon first removes as much of the cancer as possible. Next, a warmed solution of chemotherapy drugs, most commonly cisplatin, is infused into the chest cavity, left for a period of time, and then washed out. This delivers the chemotherapy drugs directly to the sites where cancer cells are most likely to be and reduces the likelihood and severity of side effects.