What Is Mesothelioma?

Mesothelioma is a rare form of cancer that affects cells (called mesothelium) that line the pleura (chest cavity) or the peritoneum (abdominal cavity). Most people with mesothelioma have worked in jobs where they breathed in fibers of asbestos. Others have been exposed to asbestosis fibers in their homes, often without knowing it.

The disease process

Irritant dust particles present in some work environments or homes can cause chronic lung disease, generally called pneumoconiosis. The type of pneumoconiosis caused by asbestos fibers is called asbestosis. Asbestos is a mineral fiber that was commonly added to many products in the past to strengthen them, as well as to provide heat insulation and fire resistance. Asbestos in a home or building is not hazardous until it becomes damaged over time, releasing asbestos fibers into the air. Breathing in these fibers can cause scarring in the lungs and gradual destruction of the lung tissue. Over time, asbestos may trigger the development of mesothelioma.

Because of the long delay between exposure to asbestos and the onset of mesothelioma, exposure that occurred even decades ago (for example, among shipyard workers during World War II), may place a person at risk for developing this type of cancer. An exposure lasting only one or two months can result in mesothelioma developing 30 or 40 years later. People diagnosed with mesothelioma today were usually exposed in the 1940s through the 1970s.

Survival rates

Like most cancers, the outlook for recovery (prognosis) often depends on how early the disease is diagnosed and how aggressively it acts and is treated. Patients are often told that the expected survival time is only 12 to 18 months. However, specialists at leading cancer centers often have better statistics. For example, the five-year survival rate has approached 40 percent for selected patients at Brigham and Women's Center in Boston.

How Is Mesothelioma Treated?

Like most cancers, the outlook for recovery (prognosis) for people with mesothelioma depends on when the disease is diagnosed and how aggressively it is treated. The treatment plan depends on the stage and location of the cancer, as well as the age and desires of the patient. Treatment generally involves some combination of:

• Surgery (to remove the cancer or buildup of fluid)
• Radiation (the use of high-energy X-rays to kill cancer cells)
• Chemotherapy (drugs that kill cancer cells)

Surgery

Surgery is a common treatment for mesothelioma. The doctor may remove part of the lining of the chest (pleurectomy) or abdomen, and some of the surrounding tissue to get out all of the cancer. Depending on how far the tumor has spread, a lung may also be removed in an operation called a pneumonectomy. Sometimes part of the diaphragm is also removed.

If fluid has collected in your chest or abdomen, your doctor may drain the fluid out by putting a needle into the area and using gentle suction to remove the fluid. Removal of chest fluid for diagnosis or for therapy is called thoracentesis; removal of abdominal fluid is called paracentesis.

Radiation

Radiation therapy uses high-energy X-rays to kill cancer cells or reduce the size of the tumor. Radiation may be administered from a machine outside the body (external radiation therapy) or by inserting materials that produce radiation (radioisotopes) through thin plastic tubes into the cancer area (internal radiation therapy).

Chemotherapy

Chemotherapy uses drugs to kill cancer cells. The drugs may be taken as pills or they may be put into your body by a needle into a vein or muscle. Chemotherapy is called a systemic treatment because the drug enters the blood, travels through the body (that is, through your entire system), potentially killing cancer cells anywhere in the body. For mesothelioma, chemotherapy may also be put directly into your chest (intrapleural chemotherapy). Recent approval of a new program using pemetrexed (Alimta®) and gemcitabine (Gemzar®) have shown beneficial results and good tolerability.

Treatment by stage

Therapies will vary according to the stage of disease, which is determined at the time of diagnosis. If the cancer is localized (found in only one place in the chest), treatment probably will consist of surgery to remove the tumor and surrounding tissue. If the cancer is present in a larger area, treatment may involve more extensive surgery, external radiation and/or chemotherapy.

Treatment for advanced disease may include thoracentesis or paracentesis to reduce discomfort, as well as drugs placed directly into the chest to prevent further fluid buildup. Surgery and radiation may relieve symptoms, and various types of chemotherapy may be used.

Other treatments

Not all patients respond to standard therapy, and some standard treatments have undesirable side effects. For these reasons, new approaches to therapy are currently being evaluated in clinical trials. These new therapies often combine traditional treatments with something entirely new.

Recent studies reported at the American Society of Clinical Oncology showing that combining a new drug called Alimta® (pemetrexed) with cisplatin have shown good results.

Clinical trials

Clinical trials are currently underway to test new drugs and procedures to fight mesothelioma.