Mayo Clinic: Asbestos exposure most significant risk factor for mesothelioma

DEAR MAYO CLINIC: What causes mesothelioma, and how is it different from lung cancer? Are there any treatments or ways to slow its progression?

ANSWER: Mesothelioma is a rare type of cancer, with about 3,000 new cases reported each year in the United States. It is much less common than lung cancer. Unlike lung cancer, mesothelioma does not start within the lung tissue. It arises from the mesothelium that forms the outside lining of the lung, also called the pleura. However, mesothelioma may spread into the lungs.

Rarely, it can also arise from the lining of the abdominal cavity or other internal organs. The most common treatment for mesothelioma is chemotherapy, but a combination of different therapies can be used. Research investigating possible new treatment options is underway.

The exact cause is unclear, but the most significant risk factor for developing mesothelioma is asbestos exposure. Asbestos is a fibrous mineral found naturally in the environment. Asbestos fibers are strong and heat resistant, making them useful in a wide variety of products, including building insulation and flooring.

When breaking up asbestos — during the mining process or the removal of asbestos insulation, for instance — dust can be created. If you inhale or swallow the dust, the asbestos fibers settle in your lungs or stomach, where they can cause irritation that may lead to mesothelioma. Exactly how this happens isn’t understood. It can take 30 to 40 years or more for mesothelioma to develop after asbestos exposure.

Unfortunately, there’s no screening test for mesothelioma. Most patients seek medical attention when symptoms such as shortness of breath and chest pain develop. These symptoms often don’t appear until the disease is in its late stages. At that point, treatment options are limited. People with mesothelioma are rarely cured. The goal of treatment typically is to control the disease as long as possible.

For most patients with late-stage mesothelioma, treatment involves chemotherapy. More aggressive treatment options combining surgery with chemotherapy and radiation are limited to early-stage mesothelioma patients, who can tolerate these therapies.

For those who can tolerate it, the goal of surgery is to remove all visible disease — a complex and difficult task. In addition, the benefits of surgery depend heavily on the addition of chemotherapy and radiation therapy. Many people have trouble with the side effects of those treatments. Despite using a variety of treatments, long-term survival remains low for patients with mesothelioma, with a five-year survival rate between 5 and 10 percent.

A team approach to treatment can be helpful. Such teams often include lung physicians and lung surgeons, physicians who specialize in cancer care, pathologists who work with the lab tests and experts in imaging exams. The goal is to identify the best possible treatment options for each patient.

Researchers are exploring possible new treatments for mesothelioma. For example, researchers at Mayo Clinic are working on a clinical trial that uses the measles virus to fight mesothelioma, as has been done with other hard-to-treat cancers such as multiple myeloma. Although the research is still in its early stages, investigators have seen interesting responses to potential new therapies and are optimistic that treatment for mesothelioma can be improved. — Dr. Tobias Peikert, pulmonary and critical care medicine, Mayo Clinic, Rochester, Minn.

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