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.
Such epidemiological questions are vexing in part because mesothelioma tends to appear 30 to 50 years after asbestos exposure. That can also foil diagnosis, says Dr. Pass. Doctors often confuse the earliest symptoms, including shortness of breath, with heart disease or a sign of aging, so months often pass before a patient is correctly diagnosed. Delayed diagnosis is just one of several factors that makes mesothelioma a devastatingly effective killer, says Dr. Pass. It’s hard to remove surgically and is resistant to radiation and chemotherapy. Overall, fewer than 10 percent of patients survive five years after diagnosis.
Until recently, many doctors advised patients to forego grueling treatments and just live the rest of their lives as comfortably as possible. But Dr. Pass says they’re making progress. New combinations of chemotherapy agents have been found to shrink tumors up to 40 percent of the time, and surgeons are perfecting techniques for removing diseased tissue. Selective use of radiation can even delay recurrence for some patients. “Treatments are better now,” says Dr. Pass. “There is no excuse for a doctor to say, ‘There’s nothing to do.’ ” Researchers are finding ways to diagnose and track the disease, and they’re uncovering the cancer’s cellular quirks to better design new therapies.
Beginning in 1998, one of Danielle Rosinski’s lungs kept filling up with fluid. “Every year I had it drained and nothing showed up,” says Rosinski, a 66-year-old mesothelioma patient from Westland, Michigan. In 2003, her pulmonologist suggested pleurodesis—sprinkling talc into the space between her chest and lungs to keep fluid from accumulating. That’s when he saw the cancer. “When he told me I could live a year, well, that was a big blow,” says Rosinski, noting she’s reached nearly three years now.