Definition Malignant mesothelioma is a soft tissue tumour that can develop in the linings of the chest or belly.
What is going on in the body? Mesothelioma is an aggressive cancer that is almost always linked with exposure to asbestos. One site of this cancer is the lining that surrounds the lungs, called the pleura. Mesothelioma can also affect:
the chest wall cavity
the muscle that separates the chest and stomach cavities, which is called the diaphragm
the inside of a person's chest, or thorax
The cancer can also develop in the layer of cells that lines the stomach cavity and surrounds many pelvic and stomach surfaces. The tumour can cause a single large invasive mass or many tumours, or can invade surrounding tissue. This can include the chest wall, heart surface, diaphragm, liver, abdominal and pelvic organs, or other vessels and nerves.
This kind of cancer is very hard to cure. It often does not respond to surgery. The tumour can grow at the original site as well as spread through the blood to other organs such as the liver. For some people, the disease is so aggressive and widespread that there is no viable form of treatment. Other people might undergo surgery, radiation, chemotherapy, or a combination of these treatments.
What are the signs and symptoms of the disease? Mesothelioma that affects the pleura, the thin membrane that protects the lung, can cause these symptoms:
shortness of breath
chest wall pain
wheezing, hoarseness, or cough
mass or calcium deposits in the pleura
fluid within the lining of the lung, known as pleural effusion
collapsed lung, in severe cases
many tumour masses, in severe cases
evidence that the disease has spread, in severe cases
Tumours that affect the membrane that lines the stomach cavity and covers most of the internal organs, called the peritoneum, often do not cause symptoms until they are at a late stage. Symptoms include:
pain
an abnormal build up of fluid in the stomach
weight loss
a mass in the stomach that can be felt when the area is pressed
problems with bowel function
In severe cases of the disease, the following symptoms may be present:
low blood sugar level
a disorder causing widespread clotting in the smallest blood vessels and severe bleeding in many body organs, called disseminated intravascular coagulation
inflammation and blood clots in the veins, called thrombophlebitis
blood clots in the arteries of the lungs, called pulmonary emboli
spread of the cancer to the liver with jaundice, a condition where the skin has a yellowish tint
elevation of the blood platelet count, known as thrombocytosis
severe build up of fluid in the stomach
high volume of fluid within the membrane that lines the lung, known as pleural effusion
This disease does not usually spread to the bone, brain, or adrenal glands. Pleural tumours are mostly found only on one side.
What are the causes and risks of the disease? The link between asbestos and this form of cancer was suspected as early as the 19th century. People who have mined, milled, or worked with asbestos are at high risk for this disease. Also, labourers who work with plumbing, boilers, or other heating equipment that use asbestos are at risk. Others who do not work directly with asbestos but are in the area where the substance is being used are also at risk. This may include carpenters, electricians, or welders. People who live with asbestos workers, such as spouses and children, also have a higher risk of getting this cancer.
It takes 30 to 40 years from the time of asbestos exposure for mesothelioma to develop. In Australia 1400 cases of mesothelioma were recorded over the past 3 years. It is estimated that Australia would produce 13,000 cases of mesothelioma and another 30,000 to 40,000 cases of asbestos - realted lung cancer by 2020. Australia has one of the highest rates of asbestos related disease in the world. Since the primary means of exposure has been due to working with asbestos, the rate of this cancer is 3 to 5 times higher in men than in women. People who are exposed to asbestos and smoke cigarettes are many times more likely to develop the disease. The disease is extremely rare in children.
What can be done to prevent the disease? Asbestos has been regulated as a priority existing chemical (PEC). It has been regulated in Australia through various state and territory legislation relating to occupational health and safety, dangerous goods and to a limited extent through environmental protection. General legislative measures currently taken for the control of asbestos include:
restricting use through prohibition (often subject to exemptions) of imports and sale, manufacturing or use and/or by licensing certain activities such as import and waste disposal;
regulating its use in the workplace through specific restrictions on the method or standard of carrying out an activity, such as prohibitions against exceeding prescribed exposure standards;
labelling requirements for asbestos and asbestos-containing products;
controls on methods for packing and transportation
In the past, asbestos was used as a fire retardant and an insulator. Other products are now used in its place. The controversy involving exposure to different forms of asbestos continues.
There are two major types of asbestos called chrysotile and amphibole. It is thought that the amphibole form of asbestos is to blame for causing mesothelioma. However, asbestos is still being removed even if it is clearly of the chrysolite variety. Removal has already taken place in schools and other public buildings. The hope is that these measures will greatly reduce the occurrence of this cancer. There may be other causes of this disease. Mesothelioma also has been linked to exposure to silicate-type minerals in other parts of the world.
How is the disease diagnosed? A doctor will have a good idea that the disease is present by performing a physical examination, chest X-ray, and a CAT scan. The diagnosis is confirmed with a biopsy. A large piece of tissue is needed for the biopsy.
There are several ways to take a tissue sample, called a biopsy. One is through a needle, called a needle biopsy. Also, an incision can be made in the chest, which is called a thoractomy, and the tumour removed. The area in question can also be viewed with a scope, known as a thoracoscopy or peritoneoscopy, and the tissue biopsied in this way.
In making the diagnosis of mesothelioma, biopsy results must clearly show that the abnormal cells do not stem from other types of cancer. Tissue stains normally used to do this often do not work for this type of cancer. Immunohistochemistry, which looks at the specific cells within the tumour area, or electron microscopy, which uses a special microscope to examine very small cells, is needed to establish a tissue diagnosis.
Staging of mesothelioma that affects the pleura can be important in deciding on treatment.
Stage I means that the cancer affects the outer edges of pleura on only one side of the body.
Stage II means that the cancer has invaded the pleura, and may have spread to the oesophagus, heart, or structures in this region.
Stage III means the cancer has spread to the membrane lining the abdominal cavity, called the peritoneum.
Stage IV means the cancer has spread throughout the body via the bloodstream.
Tumours that affect the peritoneum often occur in more than one place. These tumours are not staged in this way. The cancer is usually confined to the belly. CT might reveal substantial fluid, multiple masses, liver cancer, or involvement of multiple sections of the bowel. There is no specific laboratory test for mesothelioma.
What are the long-term effects of the disease? This is a highly aggressive tumour that is often deadly. Occasional cases of benign peritoneal mesothelioma type tumour have occurred. Current treatment of malignant mesothelioma is designed to make the person with cancer comfortable. Long-term survival cannot usually be expected.
What are the risks to others? This disease cannot be passed from one person to another. The exposure to the asbestos that caused the cancer occurred many years to several decades before the disease appeared. People who live with asbestos workers also have a higher risk of getting this cancer.
What are the treatments for the disease? Treatment can involve surgery, radiation or chemotherapy, or a combination of these. To ease symptoms of this disease, the following may be used:
narcotic analgesics
removal of pleural or peritoneal fluid
intravenous glucose
In its advanced stage, this cancer is not considered curable. In this case, treatment involves making the person comfortable. Surgery very rarely is appropriate to try to cure the problem. Surgery may stop recurrent fluid build up next to the lung as a pleural effusion.
Individuals with peritoneal mesothelioma can benefit from surgery. To treat the side effects of this cancer, operations can remove fluid build up, bowel obstruction, or other problems. It may also relieve pain linked with these conditions. If the cancer has invaded the chest wall, heart, lymph nodes, or diaphragm, surgery probably will not help. People in whom the cancer has spread to distance sites will also not be helped by surgery.
Radiation therapy can be used. This treatment is usually done to make a person more comfortable.
Drugs used for chemotherapy include doxorubicin, gemcytabine, cisplatin and others. Use of these agents is associated with a less than 50% response rate. The therapy is primarily to ease discomfort. This type of chemotherapy can be combined with radiation. It can also be given directly into the pleural or peritoneal space.
What are the side effects of the treatments? Surgery can be fatal due to the extensive nature of the operation needed.
Radiation frequently damages the lung. Significant injury to other normal tissues including the heart and liver is possible.
Single agent or multiple drug therapy can be toxic. Use of combination agents is likely to cause:
hair loss
mouth sores
diarrhoea
increased risk of infection
bone marrow suppression, where the bone marrow is not able to produce normal types and amounts of blood cells
What happens after treatment for the disease? After treatment, people will be monitored for lung, heart, and other organ function. Some people who have had a lung removed may need to continue using oxygen.
How is the disease monitored? Individuals need to be checked to see if the cancer is returning. This usually includes physical examinations, blood tests, chest X-rays, and CAT scans. There is no specific blood test that accurately predicts recurrence. Mesothelioma can come back several months to a few years later. A second tumour, independent of the first, has been known to occur, as well.
Author: Thomas Fisher, MD Reviewer: HealthAnswers Australia Medical Review Panel Editor: Dr David Taylor, Chief Medical Officer HealthAnswers Australia Last Updated: 1/10/2001 Contributors Potential conflict of interest information for reviewers available on request
