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Lung Cancer
Steven E. Weinberger MD, MACP, FRCP, ... Jess Mandel MD, FACP, in Principles of Pulmonary Medicine (Seventh Edition), 2019
Miscellaneous Factors
Exposure to radon, a gas that is a decay product of radium-226 (itself a decay product of uranium-238), is a clear risk factor for the development of lung cancer. Epidemiologic studies of uranium miners exposed to high levels of radon working in the United States and Europe prior to the 1980s, when the risk was identified, demonstrated an increased incidence of both small cell and squamous cell carcinoma (see discussion of pathology further on). The risk appears to be mitigated by improved working conditions in mines.
Exposure to much lower levels of this known carcinogen may occur indoors in homes built on soil that has a high radium content and is releasing radon into the surrounding environment. The finding of unacceptably high levels of radon in some home environments has sparked concern about the risk of lung cancer and interest in widespread testing of houses. Household levels of radon never come close to the level experienced by miners, so some uncertainty remains about the overall risk posed by exposure to household radon. However, most authorities agree there is a small but real increased risk of lung cancer associated with elevated home levels. It has been suggested that radon is the second most important factor contributing to lung cancer and is potentially responsible for 20,000 lung cancer deaths per year in the United States.
Some evidence suggests that dietary factors may affect the risk of lung cancer. Some studies have reported an association between low intake and serum levels of beta carotene, the provitamin form of vitamin A, with an increased risk of lung cancer. However, the data relating to this issue are controversial. An increased risk associated with low dietary intake of beta carotene, if it exists, is relatively minor compared with the risk posed by cigarette smoking. Three large randomized trials have failed to demonstrate a protective effect of beta carotene, alpha tocopherol, or retinoid supplementation on lung cancer risk. The issue is further complicated by data suggesting an increase in the incidence of lung cancer in some trials of individuals given supplements.
Human immunodeficiency virus (HIV) infection increases the risk of lung cancer; this association has become more important as advances in antiretroviral treatment decrease mortality from infectious causes in this population. Patients who have received radiation therapy to the thorax (e.g. as treatment for breast cancer or Hodgkin lymphoma) are at increased risk for lung cancer. Finally, in developing countries, chronic exposure to wood smoke is believed to be responsible for a sizable fraction of lung cancers, particularly among women.
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