Incidence & Risk Factors

Over 2,000 new cases of mesothelioma are diagnosed in the United States each year. Mesothelioma occurs more often in men than in women and risk increases with age, but this disease can appear in either men or women at any age. See statistics for more details.

Working with asbestos is the major risk factor for mesothelioma. A history of asbestos exposure at work is reported in the majority of cases. However, mesothelioma has been reported in some individuals without any known exposure to asbestos.

Asbestos

Asbestos is the name of a group of minerals that occur naturally as masses of strong, flexible fibers that can be separated into thin threads and woven. Asbestos has been widely used in many industrial products, including cement, brake linings, roof shingles, flooring products, textiles, and insulation. If tiny asbestos particles float in the air, especially during the manufacturing process, they may be inhaled or swallowed, and can cause serious health problems. In addition to mesothelioma, exposure to asbestos increases the risk of lung cancer, asbestosis (a noncancerous, chronic lung ailment), and other cancers, such as those of the larynx and kidney.

Since the early 1940s, millions of American workers have been exposed to asbestos dust. An increased risk of developing mesothelioma was originally found among shipyard workers, people who work in asbestos mines and mills, producers of asbestos products, workers in the heating and construction industries, and other trades people. Today, the U.S. Occupational Safety and Health Administration (OSHA) sets limits for acceptable levels of asbestos exposure in the workplace. People who work with asbestos wear personal protective equipment to lower their risk of exposure.

There is evidence that family members and others living with asbestos workers have an increased risk of developing mesothelioma, and possibly other asbestos-related diseases. This risk may be the result of exposure to asbestos dust brought home on the clothing and hair of asbestos workers.

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 pleura are often symptoms of pleural mesothelioma. Symptoms of peritoneal mesothelioma include weight loss and abdominal pain and swelling due to a buildup of fluid in the abdomen. 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.

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, including any history of asbestos exposure. A complete physical examination may be performed, including x-rays of the chest or abdomen and lung function tests. A CT (or CAT) scan or an MRI may also be useful.

A biopsy confirms a diagnosis of mesothelioma. In a biopsy, a surgeon or a medical oncologist removes a sample of tissue for examination under a microscope by a pathologist. (See Pathology Diagnosis to learn why some patients request a second opinion.)

Mesothelioma is described as localized if the cancer is found only on the membrane surface where it originated. It is classified as advanced if it has spread beyond the original membrane surface to other parts of the body, such as the lymph nodes, lungs, chest wall, or abdominal organs.

Treatment

Treatment for mesothelioma depends on the location of the cancer, the stage of the disease, and the patient's age and general health. Standard treatment options include surgery, radiation therapy, and chemotherapy. Sometimes, these treatments are combined. Standard treatment for all but localized mesothelioma is generally not curative.1 (See survival rates for median survival rates with different treatments.)

Surgery - Extrapleural pneumonectomy in selected patients with early stage disease may improve recurrence-free survival, but its impact on overall survival is unknown. Pleurectomy and decortication can provide palliative relief from symptomatic effusions, discomfort caused by tumor burden, and pain caused by invasive tumor. Operative mortality from pleurectomy/decortication is <2%, while mortality from extrapleural pneumonectomy has ranged from 6% to 30%.2

Radiation/Chemotherapy - The use of radiation therapy in pleural mesothelioma has been shown to alleviate pain in the majority of patients treated; however, the duration of symptom control is short-lived. Single-agent and combination chemotherapy have been evaluated in single and combined modality studies. The most studied agent is doxorubicin, which has produced partial responses in approximately 15% to 20% of patients studied. Some combination chemotherapy regimens have been reported to have higher response rates in small phase II trials; however, the toxic effects reported are also higher, and there is no evidence that combination regimens result in longer survival or longer control of symptoms.3

Alimta - The only FDA approved chemotherapy for malignant pleural mesothelioma (in combination with cisplatin) is pemetrexed (Alimta). In the key clinical trial that led to its approval, Alimta was combined with another chemotherapy drug (cisplatin) and compared with cisplatin alone. The patients who received the two drugs (Alimta and cisplatin) had their cancers progress (grow/spread) in 5.7 months (median). The patients who only received cisplatin had their tumors progress in 3.9 months (median). The median survival for the patients who received both drugs was 12.1 months versus 9.3 months for cisplatin only.4

Treatment Results

The Cancer Monthly database currently has the results (survival, side effects, etc.) for 42 recent therapies for mesothelioma including immunotherapy, biological therapy, radiation, chemotherapy, surgery, and alternative therapy.

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