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Mesothelioma Cancer - Aggressive and Invasive

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Mesothelioma cancer (MC) is an aggressive and invasive form of cancer, and it quickly spreads over the surface of the lungs, abdominal organs or heart. In the simplest terms, is a cancer of the mesothelium, the membrane that covers the organs in the body. It is a rare form of cancer; only 2,000-3,000 new mesothelioma cases are reported each year.

Most of the people who develop mesothelioma cancer have worked in an environment where they have inhaled particles of asbestos. Depending on what type of mesothelioma cancer is involved, how advanced it is, and other factors, life expectancy (or the median life-span after diagnosis) ranges from four months to two years. Recently, however, some advances have been made in treatment, particularly in multimodal treatment (using more than one treatment method to attack the disease) that have helped patients live longer. There are also continually new mesothelioma cancer treatments developed and combinations of treatments being tried that show promise.

Also remember that a median is just a mid-point; if the median length of life after diagnosis is a year, that means that half of the patients diagnosed live longer than a year. Many will live much longer: for an enlightening look at what that means, you can read “The Median is not the Message,” by Stephen Jay Gould.

Although exposure to asbestos has been greatly reduced since it became clear that it was responsible for serious illness, it can take 30 to 50 years for the disease to show up after exposure. (This isn’t universal, however; there are rare cases of children and adolescents who are diagnosed with mesothelioma cancer.) As a result of the delay in onset, the number of cases increased as the exposure to asbestos fibers decreased for most people.

The mesothelium is actually made up of two layers of tissue: one covers the organ, and the other forms a sac around the area, with a lubricating fluid between the layers to facilitate movement (like the expansions and contractions of a beating heart, or the expansion of your lungs as you breathe in and out.) The mesothelium has different names in different areas of the body. For example, the mesothelial membrane that surrounds the lungs is the pleura, so malignant pleural mesothelioma is cancer that starts in the membrane around the lungs. The mesothelium that lines the abdomen and covers most of the abdominal organs is the peritoneum, and the one around the heart is the pericardium. Most cases of malignant Mesothelioma cancer are pleural; the next most common type is peritoneal mesothelioma cancer.

From the mesothelium, cancerous cells can invade nearby organs, tissue, or lymph nodes, or metastasize elsewhere in the body.

The single greatest risk factor for mesothelioma cancer is exposure to asbestos. Most reported cases occur in people who have occupational exposure to asbestos, but there are some cases of second-hand exposure, where the patient is the spouse of someone who works with asbestos, and may carry the fibers home. There are cases where the patient has had no known exposure to asbestos, but these are scarce.


Asbestos and Mesothelioma Cancer

Asbestos is a fibrous mineral that has been widely used in many industrial products since the late 1800s, and especially since World War II. Because heat and chemical exposure do not affect it, and it does not conduct electricity, it has been used in products like insulation, roofing shingles, flooring materials, cement, brake linings, and fabrics. Floating particles of asbestos – often released during manufacturing, or more recently, when asbestos-containing materials are removed from buildings – can be inhaled or swallowed; these particles can cause serious illness.

In addition to its link with Mesothelioma cancer, asbestos exposure can increase the risk of lung cancer and other forms of cancer, as well as asbestosis, which is a non-malignant, chronic respiratory illness. Tobacco use does not appear to exacerbate the risk of Mesothelioma cancer when combined with asbestos exposure, but the combination does significantly increase the risk of lung disease in general.


Other possible causes

For those patients with little or no documented exposure to asbestos, there are several possibilities. First of all, it has not been determined how much asbestos exposure is required to cause MC; it may be that very small amounts (that would perhaps never be noticed) can cause the disease.

Zeolite is another fibrous mineral that is not asbestos; it has been implicated as the probable cause of an epidemic of MC in a small village in Turkey.

MC has also been known to occur in conjunction with chronic inflammation and scarring caused by other respiratory illnesses. It is also likely that there is a genetic component to the development of the illness; it tends to run in families, and while all of the family members have exposure to asbestos, MC only occurs in a very small percentage of people who were exposed to it occupationally.

Radiation therapy could also be a cause; MC has been associated with radiation treatments for other illnesses.

Other possibilities have been suggested, but not proven. They include chemical exposure and viral infection, which have caused malignant MC in some animal studies.


Mesothelioma Cancer Symptoms

The first symptoms of pleural MC may be chest pain or shortness of breath; some people may also be hoarse or have difficulty swallowing, or coughing up blood. Also, more than half of the patients with pleural MC have lower back pain or pain at the side of the chest.

Usually, the first symptom of peritoneal MC is abdominal pain or swelling, which may look like weight gain around the waist. Because the first signs of the disease are-often flu-like symptoms, many people are either diagnosed accidentally, when a tumor is discovered in the process of diagnosing unrelated symptoms, or are not diagnosed at all until the cancer is so advanced that it causes abdominal swelling. Other symptoms are weight loss, nausea, lack of appetite, and weakness.


Mesothelioma Cancer Diagnosis

There are various tests used to diagnose MC once your doctor thinks you may have it:

Medical history and physical examination

First, your medical history will be taken to establish when symptoms occurred, and whether there are any factors in your history or environment that would put you at greater risk for the disease. This may help determine if you have been exposed to asbestos at some point.

There will also be a thorough physical exam, in which the doctor looks for signs of malignant MC or other health problems. Pleural mesothelioma will often cause pleural effusion, or fluid in the chest cavity; fluid in the peritoneum or the pericardium (which can be caused by mesotheliomas in those areas) can also be detected by an exam.

Imaging

Chest x-rays can show irregular thickening of the pleura, calcifications (or mineral deposits) in the pleura, lowering the spaces between the lobes of the lungs, or fluid in the pleura. Often, these symptoms are associated with asbestos exposure that leads to malignant MC.

X-rays, CT (computed tomography) scans and MRI (magnetic resonance imaging) scans can help locate the cancer and determine its size and extent. CT and MRI scans both take multiple images of the scanned area from different positions, and use computer processing to produce detailed images that are cross-sections. CT scans use x-rays, sometimes with the injection of a non-toxic dye (to highlight details); the MRI uses magnetic fields to create its images.

Testing fluid and tissue samples

If your doctor sees that fluid has collected in the mesothelial tissue, it can be sampled with a needle and tested. Analysis of the fluid can provide more information about the cause of the effusion, and may show the presence of cancer cells. Using fluid to diagnose mesothelioma cancer is not as precise as using tissue samples, though, so it may be necessary to follow the sampling of fluid with a tissue biopsy.

If there is a tumor, a tissue sample can be taken using thoracoscopy or laparoscopy, where a thin tube with a camera connected to it can be inserted into the chest or abdomen to see the tumor and get a sample of it. (Fluid can also be collected this way.) The procedure requires only small incisions.

Surgery

Surgery can be used to remove part or all of a tumor from the chest cavity or the abdomen. The procedure of opening the chest cavity is called thoracotomy; a laparotomy is the opening of the abdominal cavity.

Oral exploration

If a patient might have pleural mesothelioma, a bronchoscopy may be performed. This is where a flexible lighted tube is inserted through the mouth into the trachea and the bronchi to look for abnormal tissue and take samples.

Lymph Nodes

Another procedure your doctor may recommend is a mediastinoscopy. A lighted tube is inserted under the sternum (the breastbone) into the chest from the neck. It is possible to see the lymph nodes using this procedure, and to take samples to analyze for malignancy.

The lymph nodes are masses of immune system cells that are about the size of a bean. They help the body fight infection and cancer. Examining the lymph nodes can determine whether the cancer has spread or not; also, because lung cancer spreads to the lymph nodes more often than mesothelioma, it may help distinguish between lung cancer and mesothelioma.

Even with tissue samples, it has traditionally been difficult to see the cells well enough to distinguish mesothelioma from different types of cancer. One of the biggest problems in diagnosing mesothelioma is that it can look just like other kinds of cancer at first.

A recent breakthrough in diagnosis that will undoubtedly have an effect on the series of diagnostic tests above was reported in November 2003.² A new blood test is being developed that can detect the presence of high levels of a distinct kind of molecular marker which is peculiar to mesothelioma, SMR (or soluble mesothelin-related proteins). In one trial, 84% of the mesothelioma patients showed high levels of SMR, while less than 2% of those with other forms of lung cancer did.

Even more promising than being able to diagnose mesothelioma in a minimally invasive way is the possibility of predicting mesothelioma in people who have no symptoms. SMR levels can be higher several years before the onset of symptoms, so by doing a blood test on people who have been exposed to asbestos, it is possible to find the disease while the chances of treating it successfully are much higher.

Mesotheliomas usually fall into one of these three types:

  1. epitheloid (making up about 50%-70% of the total occurrences)– this has the best chance of survival
  2. sarcomatoid (7%-20%) – this has the worst chance for survival.
  3. mixed or biphasic (20%-35%) – this falls between the other two

Treatment options are the same for all types.

There is a type of tumor that was originally called benign mesothelioma, because it appeared to form in the same location as malignant mesothelioma. These are actually fibrous tumors that are usually benign, although they can become cancerous. Doctors now understand that they don’t originate from mesothelial cells, but from tissue under the mesothelium, so they are not related to malignant mesothelioma. Whatever their source, however, they are not easy to differentiate from malignant mesothelioma without biopsy, so they need to be mentioned in this context.

“Mesothelioma, Questions and Answers” National Cancer Institute web site,

“Asbestos Exposure: Questions and Answers” National Cancer Institute web site,

“What is Malignant Mesothelioma?” American Cancer Society

“UNC Radiology Teaching File”



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²“Asbestos Cancer Breakthrough”, web site of the Pacific Northwest Research Institute,

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