What Is It?
Malignant mesothelioma is a rare form of cancer that is diagnosed in approximately 3,000 people each year. The disease usually affects the thin membrane that lines the chest cavity and the lungs. This membrane is called the pleura. It also can affect the lining of the abdominal cavity, called the peritoneum, and, very rarely, it affects the lining around the heart, called the pericardium.
Most cases of malignant mesothelioma are caused by exposure to asbestos, a naturally occurring mineral that was used in a variety of industries. A small percentage of cases have been linked to exposure to a mineral silicate called zeolite or to a type of radiation contrast dye (Thorotrast) that was used before 1960 to help blood vessels show up on X-rays. In a few cases, the cause is unknown.
People exposed to asbestos for a long time or exposed to high levels have an increased risk of developing malignant mesothelioma, but even people exposed for a very short time can develop this disease. The disease develops at least 15 years (typically 20 to 40 years) after exposure to asbestos. People usually are diagnosed with this disease between ages 50 to 70. More men than women get this cancer, probably because men are more likely to have worked in the industries that use asbestos.
There are three main types of malignant mesothelioma: epithelial, sarcomatoid and mixed. The epithelial type is the most common.
About 90 percent of people who are diagnosed with malignant mesothelioma have chest pain or shortness of breath as the first symptoms of the disease. Chest pain is caused mainly by the cancer itself, which irritates nerve cells in nearby tissues. Less severe chest discomfort and shortness of breath generally are caused by a collection of fluid between the two layers of the pleura in the chest, not by the cancer itself. This collection of fluid is called a pleural effusion. People with mesothelioma that develops in the abdominal lining can have abdominal pain and swelling caused by an accumulation of fluid in the abdominal cavity. Other possible symptoms include cough, fatigue and unexplained weight loss.
Your doctor will ask about your symptoms and your medical history before doing a complete physical examination. Tests usually are needed because the more common symptoms of chest pain and shortness of breath may come from many causes. These tests include an electrocardiogram (EKG), a chest or abdominal X-ray, depending on your symptoms and your physical exam. If these tests show any abnormalities of the lungs or pleura, you will need a computed tomography (CT) scan or a magnetic resonance imaging (MRI) scan. These imaging studies allow the physician to determine the size, location and extent of any tumor in the chest or abdomen.
If you have fluid in your chest or abdomen, a thin needle may be used to remove a small sample of the fluid for examination. This procedure, called fine-needle aspiration, also may be used to drain the fluid to relieve symptoms such as chest pain and shortness of breath. Occasionally, mesothelioma can be diagnosed from this fluid sample alone, but usually a tissue sample (biopsy) will have to be taken, too. The tissue sample can be obtained with procedures called a thoracoscopy or video-assisted thoracoscopy (VAT) for a pleural tumor or with a procedure called laparoscopy for an abdominal tumor. In both procedures, a tubelike instrument inserted through a small incision allows the physician to view the tumor and collect a tissue sample. You also may need a procedure called a bronchoscopy or a mediastinoscopy so the doctor can look for masses in the lung airways caused by other tumors or can remove tissue samples from lymph nodes.
Once the diagnosis of malignant mesothelioma has been confirmed, the next step is determining how far the tumor has spread (called staging). Imaging studies, such as computed tomography (CT) and magnetic resonance imaging (MRI), are used to assess the stage of the disease and determine the most appropriate treatment. There are four stages of malignant mesothelioma, with the lowest stage — stage I — having the best prognosis (outlook). In stage I, the tumor is limited to the pleural lining on one side of the chest without any signs of having spread. If the disease returns after being treated successfully, it is called recurrent mesothelioma.
Stage I also is called localized disease, whereas stages II to IV are called advanced disease.
Once it develops, this type of cancer will continue to grow and spread until it is treated.
To reduce your risk of malignant mesothelioma, you should avoid exposure to asbestos. Because there is no safe level of asbestos exposure, any asbestos exposure is too much. In your home, especially if it is an older home, have an expert check for areas of exposed asbestos-containing insulation or other areas of deteriorating asbestos. These areas must be removed professionally or safely sealed off. Workers who routinely deal with asbestos-containing materials should use approved measures to limit their exposure and to keep from bringing asbestos dust home on their clothing.
Malignant mesothelioma is a difficult disease to treat. The cancer can spread easily to nearby organs. If the tumor has spread, it is nearly impossible to remove the entire tumor surgically. In addition, it has been difficult to test the effectiveness of different treatments because there are relatively few cases of malignant mesothelioma.
The primary treatment options for malignant mesothelioma are surgery, radiation therapy and chemotherapy.
Before any surgery is considered for the treatment of malignant mesothelioma, the patient’s overall health has to be evaluated. Tests are done to make sure the cancer has not spread to distant sites, and to evaluate how well the patient’s lungs and heart are functioning. Lung tests look for any signs of lung damage from tobacco or from other diseases, including asthma and chronic obstructive pulmonary disease (COPD). These tests determine how risky surgery would be, especially if a lung needs to be removed.
Surgery for malignant mesothelioma can be aimed at long-term control of the cancer (aggressive surgery) or relief of symptoms (palliative procedures).
- Aggressive surgery — A procedure called extrapleural pneumonectomy involves removal of the pleura, the lung, the diaphragm and the pericardium. The intent of this very aggressive, complicated surgery is to remove as much of the tumor as possible. Not all centers will perform this procedure because of its complexity and because it carries a high risk of death within 30 days after surgery. Extrapleural pneumonectomy typically is done only in younger patients who are in good overall health with stage I disease. Patients are evaluated carefully to determine their ability to tolerate the surgery.
- Palliative procedures — When malignant mesothelioma is advanced, palliative procedures can be done to relieve or control symptoms such as breathlessness, which are caused by fluid or by the tumor pressing on the lung or other organs. These procedures do not cure the disease.
- A procedure called thoracentesis can be used to treat fluid collection (effusion) in pleural mesothelioma. A needle is inserted into the chest to drain the fluid, relieving breathlessness and pain. Talc may be injected into the pleural space to try to stop fluid from accumulating there. This procedure is called talc pleurodesis. Similar procedures are used to relieve fluid collection (ascites) in peritoneal mesothelioma (paracentesis).
- A procedure called pleurectomy and decortication is the surgical removal of the pleura. This procedure can be done to reduce pain caused by the tumor or to prevent the fluid from accumulating. For peritoneal mesothelioma, surgery generally is aimed at relieving symptoms.
Because of the location of malignant mesothelioma, it is extremely difficult to deliver high enough doses of radiation to kill the tumor without damaging the surrounding organs. Lower doses of radiation can help to shrink the tumor, but it is unclear whether this helps people to survive longer than if they were not treated.
Using radiation therapy after surgery has not been shown to improve survival. However, because surgery is very unlikely to remove the entire tumor, radiation commonly is done after surgery in the hopes of killing remaining tumor cells. In addition, radiation therapy can be used to relieve the symptoms of mesothelioma, including chest pain.
Chemotherapy is the use of medications to treat cancer. Chemotherapy cannot cure mesothelioma. Some chemotherapy drugs have a partial effect in some patients. Combination chemotherapy (using more than one drug at the same time) may be given in an attempt to improve the patient’s response to the medications. Some combinations have shown some promise, and some new medications are being tried.
Like radiation therapy, chemotherapy may be administered after surgery in an attempt to kill cancer cells that could not be removed during the procedure.
Treatment by Stage
Stage I (localized) mesothelioma — If a patient wants aggressive treatment and is fit enough to have surgery, some centers may do an extrapleural pneumonectomy. Another surgical option is pleurectomy and decortication, which is sometimes done to relieve some of the symptoms of mesothelioma. Both of these procedures may be followed by radiation therapy or chemotherapy.
Stages II, III and IV (advanced) mesothelioma — Pleurectomy and decortication may be done to relieve symptoms in pleural mesothelioma. Other procedures such as thoracentesis may be done to drain fluid (pleural effusions) and prevent them from recurring. Radiation therapy and/or chemotherapy also may be administered for symptom relief.
Recurrent malignant mesothelioma — There is no standard treatment for recurrent mesothelioma. Generally, treatments are considered that were not used the first time the disease was treated.
Clinical Trials and Future Treatments
New treatments for malignant mesothelioma and possible preventive measures, such as a vaccine, are being evaluated in clinical trials, and the future holds some promise. Clinical trials are research studies that evaluate new treatments for safety and effectiveness. There are no guarantees that a new treatment will work, and there are some risks. However, a clinical trial is not undertaken unless the researchers believe the treatment may have some value.
Here are some of the treatments for malignant mesothelioma that are being evaluated:
- Combination chemotherapy — Different combinations of chemotherapy drugs have been tried with mixed results.
- Intracavitary chemotherapy — Putting chemotherapy drugs directly into the pleural or peritoneal space is being researched because of its advantage over traditional chemotherapy. Because the drug is placed directly into the cavity, much greater doses can be given to patients without causing severe side effects. Some studies have shown this therapy to control effusions and reduce tumor size.
- Brachytherapy (intracavitary radiation therapy) — In this treatment, a radioactive substance is placed directly into the pleural or peritoneal space.
- Multimodality therapy — Multimodality therapy is any combination of surgery, radiation therapy and chemotherapy.
- Gene therapy — In this approach, a virus that has been genetically altered is introduced into the tumor. The virus infects the cancerous cells and makes them vulnerable to anticancer drugs.
- Immunotherapy — Treatments that stimulate the body’s immune system to fight cancer cells are called immunotherapy.
When To Call A Professional
Call your doctor promptly for an evaluation if you have any of the symptoms of lung cancer, especially if you have worked in an industry with high exposure to asbestos. If you have shortness of breath or chest pain, you should call your doctor for an evaluation as soon as possible.
Malignant mesothelioma usually is advanced by the time it is diagnosed so the outlook usually is poor. On average, the survival time after diagnosis is about one year. However, several factors affect the prognosis, including the extent of the tumor and the age and health of the patient. In some cases, survival time can be increased to two to five years or more with early detection and aggressive treatment. Improved treatments should be available in the near future.
Diseases and Conditions Center
All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.