A Cunning Predator
Therapies improve for asbestos-caused cancer.
About 3,000 Americans will be diagnosed with mesothelioma in 2006, and the rising incidence of mesothelioma outside the United States isn’t expected to peak for another 10 to 20 years. While lung cancer affects the airways of the lung itself, pleural mesothelioma affects the tissues lining the lung and the chest and accounts for the majority of mesothelioma patients. Mesothelioma can also grow across the thin mesothelial tissue that lines the abdomen (peritoneum) or, rarely, the heart or testicles.
Mesothelioma is unusual in that it’s tightly linked with an environmental cause—asbestos exposure, which accounts for more than 80 percent of cases. A variety of migration mechanisms have been proposed to explain how inhaled asbestos fibers reach the pleural surface, but none have been proven. While inhaled asbestos fibers can lead to pleural mesothelioma, it’s believed that peritoneal mesothelioma develops from asbestos fibers that are swallowed and become lodged in the digestive tract. If a person has been exposed to asbestos, smoking greatly increases his or her risk of asbestos-related lung cancer, though smoking does not appear to affect pleural mesothelioma risk. Research also points to a possible connection between asbestos and laryngeal cancer.
View Illustration: Mesothelioma: Cause & EffectMost mesothelioma patients worked or lived in a place where they were exposed to asbestos. Brauch handled asbestos-containing materials as a teenager during a summer contractor job, and later while refinishing a house.
Researchers believe asbestos triggers cancer in several ways, says Harvey Pass, MD, a leading mesothelioma expert and chief of thoracic surgery and thoracic oncology at New York University Medical Center. The mineral’s microscopic fibers may physically injure cells during replication, causing genetic changes that lead to cancer. Asbestos fibers may also contain elements that chemically interact with cells, damaging genetic material and thus leading to cancer. Finally, the fibers may trigger immune system changes that lead to cancer.
Typical mesothelioma patients worked in shipyards or as miners, but Brauch’s story isn’t unusual, says Jill Dyken, PhD, an environmental health scientist with the federal Agency for Toxic Substances and Disease Registry. Family members of miners and defense workers have also developed the disease—many with relatively little exposure. “We don’t know what level of exposure is enough to cause mesothelioma,” says Dr. Dyken.