Why Only Some Smokers Get Cancer
Surprisingly, despite the strong link, only a fraction of smokers will ever develop lung cancer in their lifetimes. There are several possible explanations why some smokers avoid this deadly disease while others are not so fortunate.
Cigarette Chemicals Cause Cancer
According to the National Cancer Institute, tobacco smoke has more than 7,000 chemicals. To date, we know at least 250 of them are harmful and 69 can cause cancer.
Research suggests that nicotine, the addictive ingredient in cigarettes, may play a direct role in activating cells to become cancerous. Nicotine can stimulate cells to grow fast and prevent them from dying when they should. Nicotine also contributes to new blood vessel development, which helps to bring nutrients to cancer cells so they can grow.
Genetics Contribute to Cancer
There are genetic components to lung cancer risk. Gene variations may increase the likelihood a smoker will become addicted to cigarettes, thus more likely leading to cancer, or directly increase their risk of developing lung cancer.
In several 2008 studies, researchers found that individuals with a specific genetic flaw had a 30 percent greater risk for lung cancer. Individuals who had two copies of this altered gene had a 70 percent greater chance. The study results were somewhat mixed on whether these same mutations affect a person's tendency to become addicted. The gene variations may lead some smokers to smoke even more because of the effect smoking has on the brain's reward center.
In another study, researchers measured levels of a specific biomarker (a biologic feature that helps measure the presence or progress of disease) in smokers' urine. This biomarker indicates tissue absorption or retention of a cancer-causing chemical in tobacco. Those with the highest levels were two times at greater risk for developing lung cancer. Smokers who had the highest levels of both nicotine and this biomarker had an 8.5 percent higher risk.
Other Cancer Risk Factors
Radon, exposure to asbestos and other toxic substances, air pollution, age, certain lung diseases, and personal or family history of lung cancer also affect a smoker's likelihood of developing lung cancer.
Regardless of smokers' individual risk factors, quitting smoking has many health benefits, not the least of which is reducing the risk of developing cancer.
National Cancer Institute. "What You Need To Know About Lung Cancer." Web. 26 July 2007.
National Cancer Institute. "Harms of Smoking and Health Benefits of Quitting." Web. 12 January 2011.
Swaminathan, Nikhil. "Why Some Smokers Get Lung Cancer--And Others Are Spared." Scientific American. Web. 4 April 2008.
The Economist. "Smoking out the smoking gene." Web. 3 April 2008.
Medical News Today. "Urine Test May Predict Lung Cancer Risk In Smokers." Web. 20 Apr 2009.
Etzel, Carol J., Ph.D., and Bach, Peter B. M.D., M.A.P.P. "Estimating Individual Risk for Lung Cancer." Seminars in Respiratory and Critical Care Medicine 32(1) (2011): 3 - 9. Medscape Medical News. Web. 12 September 2011.
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