Mesothelioma is a rare form of cancer in which malignant (cancerous) cells are found in the mesothelium, a protective sac that covers most of the body's internal organs. With rare exceptions, most mesothelioma cancers are considered malignant mesothelioma. The two major types of malignant mesothelioma are pleural mesothelioma, which concerns the mesothelium membrane that surrounds the lungs, and peritoneal mesothelioma which concerns the mesothelium layer that covers the organs in the abdominal cavity. The prognosis, therapy (including types of chemotherapy) and treatment choices are similar whether the cancer is pleural mesothelioma or peritoneal mesothelioma.
Mesothelioma Treatments and Therapies
Standard treatment for all but localized mesothelioma is generally not curative.1 Surgery and radiotherapy have a limited role in highly selected mesothelioma patients and chemotherapy is the only potential treatment option for the majority of people diagnosed with mesothelioma. Sometimes, these mesothelioma therapies are combined. Despite activity of some chemotherapy, the results are still modest, with a median survival of approximately one year. For individual patients, treatment for mesothelioma depends on the location of the cancer, the stage of the disease, and the patient's age and general health. 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 for mesothelioma, Alimta was combined with another chemotherapy drug (cisplatin) and compared with cisplatin alone. The median survival for the patients who received both chemotherapy drugs was 12.1 months versus 9.3 months for mesothelioma patients who only received cisplatin.2
Mesothelioma Prognosis and Survival
In general the prognosis of mesothelioma is poor and most studies report median survival of less than a year. However, there are long term mesothelioma survivors (both pleural and peritoneal survivors) who have survived more than 10 years. In fact, in one mesothelioma study, doctors writing about the prognosis of mesothelioma explained that long-term mesothelioma survivors do exist and their prognosis may be independent of the treatment or therapies pursued.3 If this is true, it would suggest that mesothelioma prognosis and survival may be more dependent on individual differences among patients (and perhaps the non-conventional therapies they use) and less dependent upon conventional mesothelioma treatments.
Symptoms of Mesothelioma
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 of mesothelioma may include pain, trouble swallowing, or swelling of the neck or face.
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 and 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 is often used to confirm a diagnosis of mesothelioma. Mesothelioma is described as localized if the cancer is found only on the membrane surface where it originated. It is classified as advanced if the mesothelioma has spread beyond the original membrane surface to other parts of the body, such as the lymph nodes, lungs, chest wall, or abdominal organs.
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. 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 and Mesothelioma
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. There is evidence that family members and others living with people exposed to asbestos 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.
New Directions for Treating Mesothelioma
Because conventional therapies are not curative for the overwhelming majority of mesothelioma patients, researchers are investigating new types of mesothelioma treatments and therapies. One approach that may yield promising results is anti-angiogenesis. Anti-angiogenesis is a form of therapy that uses drugs or other substances to stop tumors from making new blood vessels. Without a blood supply, the cancers cannot grow effectively. Today, there are several hundred clinical trials of anti-angiogenesis drugs under way. For example, Veglin is an anti-angiogenesis drug undergoing clinical trials at the University of Southern California's Keck School of Medicine. Under the supervision of Parkash S. Gill, M.D. and financed by grants from the Mesothelioma Research Foundation of America, a Phase I study of Veglin has demonstrated some success in patients suffering from lymphoma, sarcoma, and colon and lung cancers. Phase II studies are on-going with the hope they will demonstrate continued clinical efficacy in mesothelioma and other cancers.
Mesothelioma Treatment Results -The Cancer Monthly database currently has the results (survival, side effects, and more) for over 40 recent treatments and therapies for mesothelioma including immunotherapy, biological therapy, radiation, chemotherapy, and surgery. Click here to search for treatment results.
Unless otherwise indicated by an endnote, most of the above material was adapted from National Cancer Institute Cancer Facts - Mesothelioma: Questions and Answers 5/13/2002.
1 National Cancer Institute Malignant Mesothelioma (PDQ®): Treatment; Health Professional Version - Treatment Option Overview available here on September 30, 2005.
2 Vogelzang NJ, et al., Phase III study of pemetrexed in combination with cisplatin versus cisplatin alone in patients with malignant pleural mesothelioma . J Clin Oncol. 2003 Jul 15;21(14):2636-44.
3 Wong, C.F., et al., A Case of Malignant Pleural Mesothelioma with Unexpectantly Long Survival without Active Treatment, Respiration March/April 2002; 69, 2: 166-168.