Mesothelioma Information: Definition

Mesothelioma is a rare form of cancer. In mesothelioma, malignant cells are found in the sac lining of the chest (the pleura) or the abdomen (the peritoneum). In this disease, malignant (cancerous) cells develop in the mesothelium, a protective lining that covers most of the body's internal organs. Its most common site is the pleura (outer lining of the lungs and chest cavity), but it may also occur in the peritoneum (the lining of the abdominal cavity) or the pericardium (a sac that surrounds the heart. The majority of people with mesothelioma have a history of jobs that exposed them to asbestos, an insulation material or have been exposed to asbestos dust and fibre in other ways, such as by washing the clothes of a family member who worked with asbestos, or by home renovation using asbestos cement products.

Mesothelioma Information: Description

In the chest and abdominal cavities, as well as in the cavity around the heart (pericardial sac), there is a layer of specialized cells called mesothelial cells. These cells also surround the outer surface of most internal organs. These cells form tissue called mesothelium. The mesothelium performs a protective function for the internal organs by producing a lubricating fluid that permits the organs to move around. For example, this fluid makes it easier for the lungs to move inside the chest while a person breathes. The mesothelium of the abdomen is known as the peritoneum, and the mesothelium of the chest is called the pleura. The pericardium refers to the mesothelium of the pericardial cavity. There are three primary types of malignant mesotheliomas: Epithelioid. About 50% to 70% of mesotheliomas are of this type and have the best outlook for survival. Sarcomatoid. Approximately 7% to 20% of cases are of this type. Mixed/biphasic. From 20% to 35% of mesothelioma cases fall into this category. Approximately three fourths of all mesotheliomas begin in the chest cavity and are known as pleuralmesotheliomas. Peritoneal mesotheliomas begin in the abdomen, and make up around 10% to 20% of all cases. Mesotheliomas arising in the cavity around the heart are quite rare.

Mesothelioma Information: Signs and symptoms

Symptoms of mesothelioma may not appear until 30 to 50 years after exposure to asbestos. Shortness of breath and pain in the chest due to an accumulation of fluid in the pleural space are often symptoms of pleural mesothelioma. Symptoms of peritoneal mesothelioma include weight loss and cachexia, abdominal swelling and pain due to ascites (a buildup of fluid in the abdominal cavity).
Other symptoms of peritoneal mesothelioma may include bowel obstruction, blood clotting abnormalities, anemia, and fever. If the cancer has spread beyond the mesothelium to other parts of the body, symptoms may include pain, trouble swallowing, or swelling of the neck or face. These symptoms may be caused by mesothelioma or by other, less serious conditions.

Mesothelioma Information: Diagnosis

Diagnosing mesothelioma is often difficult, because the symptoms are similar to those of a number of other conditions. Diagnosis begins with a review of the patient's medical history. A history of occupational exposure to asbestos may increase clinical suspicion for mesothelioma. A doctor should be seen if a person experiences shortness of breath, chest pain, or pain or swelling in the abdomen. If these symptoms are present, the doctor may order an x ray of the abdomen or chest. The doctor will do a complete physical examination and take a thorough medical history. Then, one or more of the following methods may be used to ascertain whether mesothelioma is present: A physical examination is performed, followed by chest X-ray and often lung function tests. The X-ray may reveal pleural thickening commonly seen after asbestos exposure and increases suspicion of mesothelioma. A CT (or CAT) scan or an MRI is usually performed. If a large amount of fluid is present, abnormal cells may be detected by cytology if this fluid is aspirated with a syringe. For pleural fluid this is done by a pleural tap or chest drain, in ascites with an paracentesis or ascitic drain and in a pericardial effusion with pericardiocentesis. While absence of malignant cells on cytology does not completely exclude mesothelioma, it makes it much more unlikely, especially if an alternative diagnosis can be made (e.g. tuberculosis, heart failure). Diagnosing mesothelioma is often difficult, even with tissue biopsies. Microscopically, mesothelioma is often difficult to distinguish from several other forms of cancer. For this reason, certain laboratory tests are performed to help correctly diagnose mesothelioma. Some of these tests involve using antibodies to distinguish lung cancer from mesothelioma. Sometimes the tissue samples must be viewed under an electron microscope in order to get the correct diagnosis.

Mesothelioma Information: Treatment

A person with symptoms of mesothelioma will most likely seek help from a primary physician initially. During the diagnostic phase, various technicians will perform the imaging studies. A specially trained physician—a thoracic surgeon or, rarely, a pulmonologist— performs other diagnostic tests like pleural biopsy and thoracoscopy. A pathologist will view the tissue samples and make the tissue diagnosis. Following diagnosis, the patient will be offered some form of treatment, which may entail surgery, radiation therapy, chemotherapy, or a combination of these. The patient may receive care from a thoracic surgeon, an anesthesiologist, medical and radiation oncologists, and specially trained nurses who administer chemotherapy.
Treatment of MM using conventional therapies has not proved successful and patients have a median survival time of 6 - 12 months after presentation. The clinical behaviour of the malignancy is affected by several factors including the continuous mesothelial surface of the pleural cavity which favours local metastasis via exfoliated cells, invasion to underlying tissue and other organs within the pleural cavity, and the extremely long latency period between asbestos exposure and development of the disease.

Surgery

Surgery, either by itself or used in combination with pre- and post-operative adjuvant therapies has proved disappointing with a 5 year survival rate of less than 10%. It is most useful for palliation.


Radiation

Although the tumor is highly resistant to radiotherapy and chemotherapy, these regimens are sometimes used to relieve symptoms arising from tumour metastases such as obstruction of a major blood vessel.

Chemotherapy

In February 2004, the Food and Drug Administration approved pemetrexed (brand name Alimta) for treatment of malignant pleural mesothelioma.

Immunotherapy

Treatment regimens involving immunotherapy have yielded variable results. For example, intrapleural inoculation of Bacillus Calmette-Guerin (BCG) in an attempt to boost the immune response, was found to be of no benefit to the patient (while it may benefit patients with bladder cancer). Mesothelioma cells proved susceptible to in vitro lysis by LAK cells following activation by interleukin-2 (IL-2), but patients undergoing this particular therapy experienced major side effects. Indeed, this trial was suspended in view of the unacceptably high levels of IL-2 toxicity and the severity of side effects such as fever and cachexia. Nonetheless, other trials involving interferon alpha have proved more encouraging with 20% of patients experiencing a greater than 50% reduction in tumor mass combined with minimal side effects.

Heated Intraoperative Intraperitoneal Chemotherapy

A procedure known as heated intraoperative intraperitoneal chemotherapy was developed by Paul Sugarbaker at the Washington Cancer Institute. The surgeon removes as much of the tumor as possible followed by the direct administration of a chemotherapy agent, heated to between 40 and 48 C, in the abdomen. The fluid is perfused for 60 to 120 minutes and then drained. This technique permits the administration of high concentrations of selected drugs into the abdominal and pelvic surfaces. Heating the chemotherapy treatment increases the penetration of the drugs into tissues. Also, heating itself damages the malignant cells more than the normal cells.

Alternative and complementary therapies

There are no proven effective alternative therapies for mesothelioma. Because the prognosis is often poor, many patients may be interested in trying other avenues of treatment. Patients should first consult with their physicians prior to trying any of these methods. There are many well-studied complementary treatments that may increase a patient's comfort and sense of well-being. These may include meditation to aid in relaxation, massage to decrease pain, and guided imagery to help prevent nausea.

Mesothelioma Information: Prevention

The best method of preventing mesothelioma is to avoid or limit exposure to asbestos. People who might experience asbestos exposure at work include miners, insulation manufacturers, construction workers, ship builders, and factory workers.