Because lung cancer is so common, even the small fraction of lung cancer that occurs in lifelong nonsmokers represents a large number of people. For example, about 20,000 of this year’s US lung cancer deaths will be in never-smokers.
Clinical studies have shown that lung tumors in never-smokers have a different molecular profile and better response to targeted therapy than cancers in smokers, and in some respects represent a different type of cancer.
Some researchers have hypothesized on the basis of limited data that, among never-smokers, women may have higher risk of developing lung cancer than men but lower risk of dying from it.
Younger women have higher lung cancer incidence rates than men among never-smokers of European descent, and African American and Asian women have higher age-standardized lung cancer incidence rates than men.
The researchers that provided this information analyzed information on lung cancer incidence and/or death rates among nearly 2.5 million self-reported never smokers (men and women) from 13 large studies investigating the health of people in North America, Europe, and Asia.
They also analyzed similar information for women taken from cancer registries in ten countries at times when very few women were smokers (for example, the US in the late 1930s).
The incidence rate of lung cancer in never smokers approximates that of brain cancer (plus other nervous system cancers) in the SEER (Surveillance Epidemiology and End Results) registries for individuals of European descent under age 70 y.
At older ages, the incidence rates increase more rapidly than the incidence of brain cancer and become comparable to the SEER incidence rates for liver and kidney cancer.
Eighty-five to 90% of lung cancer deaths are caused by exposure to cigarette smoke and, on average, current smokers are 15 times more likely to die from lung cancer than lifelong nonsmokers (never smokers).
The researchers also show that men have higher death rates from lung cancer than women irrespective of racial group, but that women aged 40â€“59 years have a slightly higher incidence of lung cancer than men of a similar age.
This difference disappears at older ages. An analysis of lung cancer incidence and death rates at different times during the past 70 years shows no evidence of an increase in the lung cancer burden among never smokers over time.
Although some of the findings described above have been hinted at in previous, smaller studies, these and other findings provide a much more accurate picture of lung cancer incidence and death rates among never smokers.
Lung cancer is obviously a significant public health and medical problem, even beyond the overwhelming disease burden caused by tobacco smoking.
Thun MJ, Hannan LM, Adams-Campbell LL, Boffetta P, Buring JE, et al. (2008) Lung Cancer Occurrence in Never-Smokers: An Analysis of 13 Cohorts and 22 Cancer Registry Studies . PLoS Med 5(9): e185. Copyright: Â© 2008 Thun et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License.
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