Mesothelioma: The Asbestos Risk Factor When asbestos fibers are inhaled into the lungs, they tend to remain there, and with continuous long-term exposure, the fibers begin to collect at the bottom of the lungs, where they become trapped in the pleura. Over time, this can lead to cancer, especially if there are other aggravating factors like a genetic predisposition or a history of smoking. "Asbestos irritates the lining of the lung and causes inflammation, and then the inflammatory response and the secondary changes in the lungs and pleural space may eventually lead to a malignant degeneration," explains Timothy Winton, MD, associate professor of surgery and division director of thoracic surgery at the University of Alberta Hospital in Edmonton, Canada. One of the most striking things about mesothelioma is how long it takes for the disease to develop: Up to five decades may elapse from initial asbestos exposure to the development of cancer. But when mesothelioma finally develops, it often becomes very aggressive and can spread beyond the pleura to other mesothelial tissues. The average survival time for malignant mesothelioma ranges between four and 18 months, and about 10 percent of patient live at least five years after being diagnosed. In rare cases of slow-growing mesothelioma, survival can extend to 20 years.