What Causes Pleural Mesothelioma?
Pleural mesothelioma is caused by exposure to the carcinogen asbestos, which was used extensively in the past in a number of commercial, residential, and military applications. This rare cancer occurs when tiny asbestos fibers are inhaled and become lodged in the lining of the lungs and chest. Over time, asbestos fibers cause inflammation and scarring within the pleural lining. Eventually, the cells of the mesothelium can mutate and form malignant tumors.
Although rare, it is the most common type of mesothelioma, accounting for between 70 and 90 percent of mesothelioma cases annually.
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What Are the Symptoms of Mesothelioma?
The most common symptoms of pleural mesothelioma are chest pain and shortness of breath. Fluid buildup around the lungs, known as pleural effusion, is commonly associated with pleural mesothelioma and can make breathing painful and difficult. Additional symptoms include:
- Difficulty swallowing
- Persistent dry cough
- Weight loss
Similar to other types of mesothelioma, the symptoms of pleural mesothelioma can mirror other conditions. Common misdiagnoses include:
- Chronic obstructive pulmonary disease (COPD)
- Lung cancer
- Pulmonary fibrosis
- Synovial sarcomatoid carcinoma
If you are experiencing any of the symptoms above, talk to your doctor right away, especially if you know or suspect that you’ve been exposed to asbestos.
How Is Pleural Mesothelioma Diagnosed?
Pleural mesothelioma usually takes decades to manifest; the average age at the time of diagnosis is 69. The period between the original asbestos exposure and when symptoms begin to appear is called the latency period. Unfortunately, by this time the tumors have likely begun to spread, which is why it’s vital that you visit your doctor as soon as symptoms appear. Be sure to share with them any history you may have with asbestos exposure. This can assist in the diagnostic process, especially since mesothelioma is so rare and the symptoms often mirror those of other illnesses.
The diagnostic process for mesothelioma generally starts with a series of imaging tests, including chest X-rays, CAT scans, PET scans, and MRIs. Pleural thickening, fluid buildup/pleural effusions, tumors, and irregularities in lung size are usually visible with these imaging tests, which can also illustrate the size of the tumors and the extent to which they have spread.
Blood tests such as MesoMark® are used to test for the presence of mesothelin-related proteins, which can indicate mesothelioma. Your doctor may also test for cancer antigen 125, a protein biomarker found in large concentrations of cancer cells, and fibulin-3, another biomarker. The fibulin-3 blood test can help distinguish between mesothelioma and other lung diseases.
If fluid is present in the chest cavity, your doctor may take samples for cytology, or fluid analysis. A tissue biopsy is often the last step in the process and is the only definitive way to diagnose pleural mesothelioma. Biopsies are helpful for understanding what cell type is present in the tumor: epithelioid, sarcomatoid, or biphasic — a combination of the two. This information is essential for establishing a treatment plan.
Procedures for Diagnosing Pleural Mesothelioma
There are a few procedures a doctor can utilize to diagnose this type of cancer. Some more common methods of diagnosis include:
Pleural biopsy is the gold standard method for establishing the diagnosis of mesothelioma. This biopsy is performed on patients experiencing fluid buildup — pleural effusion — between their lungs and chest. A needle is inserted into the chest cavity to collect a sample of the pleural fluid and tissue to check for the presence and extent of mesothelioma.
Another type of needle aspiration, this test is used to attain a sample of the pleural fluid from the chest. It also serves as a palliative treatment to relieve discomfort caused by the excess fluid buildup.
In this procedure, a camera is used to help doctors see inside the chest cavity to take a diagnostic sample and drain excess fluid.
This camera-assisted biopsy procedure allows doctors to examine the mediastinum (the space behind the breastbone) to see if the mesothelioma has spread to the lymph nodes there.
The most invasive biopsy, this surgical procedure is used to collect a sample of the tumor from the chest cavity for diagnostic purposes. It is also used as a treatment option to remove as much of the tumor as possible.
Staging Pleural Mesothelioma
Like most cancers, pleural mesothelioma is staged from 1 to 4. Since the other types of mesothelioma (peritoneal and pericardial) are so rare, this is the only type with a formal staging system. In fact, there are three recognized staging systems for pleural mesothelioma: the TNM staging system (which stands for Tumor, Node, and Metastasis), the Butchart staging system, and the Brigham staging system.
Most doctors stage pleural mesothelioma using the TNM system, which was developed by the American Joint Committee on Cancer. The TNM system stages the cancer based on the size and extent of the tumor (T-tumor), whether the cancer has reached the lymph nodes (N-node), and the presence and extent of metastasis to other parts of the body (M-metastasis).
TNM Staging System for Pleural Mesothelioma
- Stage 1
- The tumor is localized to the site of origin. The lymph nodes are unaffected and there is no metastasis to other parts of the body.
- Stage 2
- The tumor is localized to one side of the body but extends deeper into the pleura as well as the diaphragm and/or lung. Nearby lymph nodes may be affected but there is no metastasis.
- Stage 3
- The tumor is localized to one side of the body but extends deep into the pleura, diaphragm, lung, chest wall, thoracic fascia, heart sac, and/or mediastinal fat. Nearby lymph nodes are affected and there is potential metastasis to nearby organs.
- Stage 4
- The tumor is no longer localized and is not resectable by surgery. The cancer may have spread to distant lymph nodes and there may be metastasis to organs in other areas of the body.
The Butchart and Brigham staging systems are older than the TNM system but are both still used for staging pleural mesothelioma in some cases. The Butchart system is based mainly on the location of the primary tumor, while the Brigham system stages the cancer based on whether it has spread to the lymph nodes and whether the tumor can be removed via surgery.
Pleural Mesothelioma Prognosis
The prognosis for pleural mesothelioma depends on a number of factors, such as stage and cell type, as well as the patient’s age and overall health. Patients with early-stage pleural mesothelioma may undergo surgery, chemotherapy, radiation, and other treatment procedures in an effort to eradicate the cancer and significantly extend life expectancy. However, because this type of mesothelioma is usually diagnosed at a later stage, these curative treatments may not be an option for every patient. In these cases, palliative care is deployed to maintain the patient’s quality of life.
The average life expectancy for pleural mesothelioma patients is between 8 and 21 months.
Treating Pleural Mesothelioma
Treatment options for pleural mesothelioma usually involve a combination of treatments — referred to as a multimodal treatment plan — including:
Surgery for Pleural Mesothelioma
There are two main surgical options for early-stage pleural mesothelioma patients: pleurectomy with decortication, in which the linings of the lung and chest are removed, along with any visible tumors; and extrapleural pneumonectomy, in which the entire affected lung, the pleural linings of the lung and heart, and portions of the diaphragm are removed.
If these curative surgical treatments are not available, palliative surgical procedures may be used to remove fluid that has built up around the lungs to make breathing easier and less painful. These include thoracentesis (also called a pleural tap), in which a doctor uses a needle to remove excess fluid from around the lungs; and pleurodesis, a procedure that closes the space between the outer lining of the lung and the chest wall to prevent fluid buildup around the lungs in the future.
Chemotherapy for Pleural Mesothelioma
Pleural mesothelioma patients often undergo chemotherapy either before surgery to shrink the tumors or afterward to destroy any remaining cancer cells. The most common chemotherapy treatment for this type of mesothelioma is a combination of ALIMTA® and cisplatin. Chemotherapy may also be used instead of surgery as an aggressive curative treatment or as a palliative treatment to improve quality of life for late-stage patients by slowing the growth and spread of the tumors. If for palliation, a third agent called Avastin is usually added to the combination of cisplatin and ALIMTA.
Radiation for Pleural Mesothelioma
Radiation may be used before or after surgery to shrink the tumors and reduce the spread of the cancer. It can also be used as a palliative treatment to reduce the symptoms of pleural mesothelioma by relieving chest pain and easing breathing difficulties.
Immunotherapy for Pleural Mesothelioma
Immunotherapy drugs are becoming part of the standard treatment for pleural mesothelioma. This form of treatment enhances the body’s own immune system to attack malignant cancer cells.
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