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Cancer Surveillance On-Line

Lung (ICD-9 code 162)

Lung cancer includes tumours of the trachea, bronchi and lung. Virtually all lung cancers arise in epithelial tissue, and most originate from the lining of the bronchi. Lung cancer was the second most common cancer diagnosed in Canadian men in 1994, accounting for 18% of cancer diagnoses; it ranked third in women, accounting for 12% of all new cases. The male to female rate ratio is now approximately two to one, down from about three to one a decade ago.

Tobacco smoking is by far the leading cause of lung cancer, accounting for at least 80% of all new cases in women and 90% of those in men. The average relative risk of cigarette smokers compared with that of individuals who have never smoked is about 10; relative risks for heavy smokers of long duration are higher. Many of these estimates are based on studies of individuals who smoked cigarettes that were popular decades ago, but relative risks in comparable smokers of the new filter and low-tar products are still appreciable. Furthermore, the lower levels of nicotine in many current products may result in more cigarettes smoked and more puffs per cigarette, thereby increasing exposure to carcinogens in tobacco smoke. Relative risks steadily decline following smoking cessation, with risks among long-term ex-smokers approaching those of non-smokers. The risk of lung cancer in pipe and cigar smokers is approximately double that in non-smokers. Finally, non-smokers exposed to tobacco smoke by living with a smoker are at an estimated 30-50% increased risk, and passive smoking may account for much of the lung cancer not due to active smoking or industrial exposures.

Exposure to several occupational substances is associated with an increased risk of lung cancer, specifically asbestos, arsenic, polycyclic aromatic hydrocarbons (also contained in motor vehicle exhaust), chromium, silica and nickel. Occupational exposure to radon and radon daughters also increases lung cancer risk. Domestic levels of these carcinogens in households may elevate risk, although findings have not been definitive. Ecologic studies suggest that the effect of urban air pollutants on lung cancer incidence in North America is relatively small.

A number of studies have linked high fruit and vegetable intake as well as high serum -carotene levels with a reduced risk of lung cancer, but a recent clinical trial of beta-carotene supplementation in individuals at high risk of lung cancer found increased rates among supplemented patients. Support for the hypothesis that a high cholesterol and/or fat diet increases the risk of lung cancer has been inconsistent. Alcohol consumption has been linked with increased risk in various studies, although these studies do not rule out the possibility of residual confounding by cigarette smoking.

Currently, the main hope in controlling lung cancer is through primary prevention. Strategies aimed at smoking cessation and avoidance in large segments of the population, including targeting young people for prevention programs, have the greatest potential. Economic incentives, such as increases in cigarette prices and taxes, have been shown to accelerate decreases in cigarette consumption. As the potential effects of environmental tobacco smoke have become clearer, anti-smoking measures in the workplace and public places should also have a growing impact. Routine screening for lung cancer is not effective, even in heavy smokers or other high-risk groups.


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Last Updated: 2002-02-07