Asbestosis natural history


 * Associate Editor(s)-In-Chief: Kim-Son H. Nguyen, M.D., M.P.A., Beth Israel Deaconess Medical Center, Harvard Medical School, Boston MA,

Overview
People with extensive occupational exposure to the mining, manufacturing, handling or removal of asbestos are at risk of developing asbestosis. There is also an increased risk of lung cancer and mesothelioma. Asbestosis and lung cancer require prolonged exposure to asbestos. However, cases of mesothelioma have been documented with even 1-3 months of exposure, and only indirect exposure (through air ventilation system.) Most cases of asbestosis do not present until 5-10 years after exposure to the material.


 * Malignancy is associated with asbestos exposure:
 * Mesothelioma
 * Mesotheiloma is an insidious neoplasm arising from the mesothelial surfaces of the pleural and peritoneal cavities or pericardium. 80% are pleural.
 * The tumor forms on the visceral and parietal pleura in discrete plaques and nodules, and can grow to several centimeters with minimal lung penetration. Adjacent structures including the pericardium, chest wall, and diaphragm are commonly involved.  Local lymph nodes may be involved, and distant hematogenous metastases in the liver, lung, bone and adrenals may develop.
 * Asbestos exposure is the only known risk factor for mesothelioma, involved in >70% of cases. Lifetime risk of mesothelioma among asbestos workers is 8-13%.
 * Annual U.S. incidence is 2200 cases per year. It is increasingly common in non-Western countries where there is increasing asbestos exposure.
 * Tobacco use does not increase risk
 * Patients present with increasing dyspnea, often in the 5th-7th decades of life.
 * CXR usually initially shows a large unilateral pleural effusion. Chest CT more clearly shows extent of disease.
 * Video-assisted thorascopy or open biopsy are often required to make the diagnosis.
 * Median survival is 6-18 months and is ‘’not particularly amenable to treatment.’’ Death is from respiratory failure, or due to complications of invasion of involved organs.
 * Lung cancer
 * Lung cancer is more common in patients with asbestosis
 * In one study, asbestos exposure increased relative risk of lung cancer 6-fold
 * Tobacco use increases risk of developing lung cancer in a multiplicative fashion
 * Cigarette smoking alone increased relative risk of lung cancer 11-fold.
 * Cigarette smoking and asbestos exposure increased relative risk of cancer 59-fold
 * Furthermore, a dose-response curve exists for cigarettes
 * The risk of asbestos workers dying of lung cancer increases 9-fold if they smoked 1-20 cigarettes a day, and 16-fold if they smoke >20 cigarettes a day
 * Other cancers
 * Risk may be increased for gastrointestinal, larynx, oropharynx, and kidney and other cancers. Associations have been noted in some studies.