Dear Doctor: It seems like every time I turn on the TV, there's a commercial that talks about mesothelioma. What is it, and how do people get it?
Dear Reader: Mesothelioma is a rare, aggressive and often fatal form of cancer that arises in the mesothelial cells. These are specialized cells that form a thin membrane known as the mesothelium. It covers the majority of internal organs and lines several internal cavities, including in the chest and abdomen. Its main job is to provide a slippery protective surface so when tissues come into contact, they slide and glide rather than adhere. Depending on their specific location, mesothelial cells also secrete fluids, help with fluid transport, and play a role in immune function, inflammation control and tissue repair.
The main cause of mesothelioma is exposure to asbestos, which is a generic term for certain fibrous minerals that can be spun into strong fireproof thread. Awareness of the health hazards of asbestos dates back to 1924, but it took a series of increasingly restrictive laws in the 1970s for it to finally fall out of widespread use. At that time, it became clear that even light or intermittent exposure to asbestos, whether in buildings, products or manufacturing, was risky.
Today, past asbestos exposure, much of it occupational, accounts for up to 80% of all cases of malignant mesothelioma. There is evidence that family members of people who were regularly exposed to asbestos may also have increased risk of developing mesothelioma. The disease has also been linked to a specific X-ray process used in the early-to-mid 20th century, and family history is suspected to play a role in risk.
One of the many challenges of malignant mesothelioma is that it develops decades -- in some cases up to 40 years -- after asbestos exposure. Another is that symptoms often become apparent only when the disease is advanced.
The majority of cases, up to 85%, arise in the tissues of the pleura, which is the two-layered membrane that surrounds each lung. Symptoms can include chest pain, shortness of breath and chronic cough. Some people may develop a mass in the chest wall or areas of lumpy tissue beneath the skin on the chest. For disease located in the membrane around the stomach, abdominal pain, nausea, vomiting, diarrhea, unexplained weight loss and abnormal fluid accumulation can occur. When the disease affects the membrane around the heart, which is rare, symptoms can include heart arrhythmias, chest pain, difficulty breathing and low blood pressure. The disease can also cause general weakness and exhaustion, as well as night sweats.
Treatment, which includes surgery, radiation and chemotherapy, depends on the age and health of the patient, and at what stage the disease has been diagnosed. Some patients find that alternative treatments, such as acupuncture, breath training, and relaxation and mindfulness exercises can help them to cope with breathlessness. In recent years, targeted therapies, which use drugs and other substances to directly attack cancer cells, have begun to show promise. Clinical trials for new and effective treatments are ongoing.