Lung Cancer Also Affects Nonsmokers
Article date: November 15, 2011
By Stacy Simon
The American Cancer Society devotes a lot of resources to encouraging people to quit smoking, or even better, never to start at all. Especially this time of year when the Society marks the Great American Smokeout. There’s good reason for this: Tobacco accounts for 87% of lung cancer deaths and also increases risk for other cancers, as well as chronic diseases including heart disease and emphysema.
But even though it’s less common, some people who don’t smoke get lung cancer too. Every year, 16,000 to 24,000 Americans die of lung cancer even though they have never smoked. If lung cancer in “never smokers” (defined by researchers as people who have smoked fewer than 100 cigarettes in their lifetime) had its own category separate from lung cancer in smokers, it would rank among the top 10 fatal cancers in the United States.
Given the impact of the disease, lung cancer and tobacco control research both deserve more attention, according to Michael Thun, MD, American Cancer Society vice president of epidemiology and surveillance. Thun says a perception that patients contributed to their own illness by smoking harms both smokers and nonsmokers with lung cancer.
Causes of lung cancer in nonsmokers
Even so, researchers have made a lot of progress over the past decade in understanding what causes lung cancer and how to treat it. Thun recently gave a presentation at the World Conference on Lung Cancer in Amsterdam in which he listed the main causes of lung cancer besides smoking as secondhand smoke, exposure to radon gas, exposure to carcinogens (cancer-causing agents) at work, and air pollution.
Each year, an estimated 3,400 nonsmoking adults die of lung cancer as a result of breathing secondhand smoke. Laws that prohibit smoking in public places and create smoke-free environments have been effective in reducing this danger. ACS CAN, the nonprofit, nonpartisan advocacy affiliate of the American Cancer Society, is working to expand and strengthen these laws to further protect both smokers and nonsmokers from the dangers of secondhand smoke.
However, the leading cause of lung cancer in nonsmokers according to the US Environmental Protection Agency (EPA) is exposure to radon gas. It accounts for about 20,000 deaths from lung cancer each year. Radon occurs naturally outdoors in harmless amounts, but sometimes becomes concentrated in homes built on soil with natural uranium deposits. Studies have found that the risk of lung cancer is higher in those who have lived for many years in a radon-contaminated house. Still, the lung cancer risk from radon is much lower than that from smoking.
For some people, the workplace is a source for exposure to carcinogens like asbestos and diesel exhaust. Such exposures tend to occur in jobs that are traditionally held by men. In addition, in an analysis published by the Public Library of Science Medicine, American Cancer Society researchers found that men who have never smoked have higher lung cancer death rates than women who never took up the habit. However, because there are more than twice as many women as men age 60 years and older who have never smoked, more nonsmoking women are affected by lung cancer.
While it’s long been known that both indoor and outdoor air pollution contribute to lung cancer, a recent study published in the American Journal of Respiratory and Critical Care Medicine measured the fine particulate matter that contributes to lung cancer deaths in nonsmokers. Using data from a large American Cancer Society database, the researchers concluded that even tiny amounts of increased carcinogens in air pollution significantly increased the risk. The researchers also noted that in China, where many homes have coal-burning cooking stoves and poor ventilation, lung cancer rates are especially high among nonsmoking women.
Lowering lung cancer risk
Nonsmokers have already eliminated their greatest risk factor for lung cancer. Male smokers are about 23 times more likely and female smokers about 13 times more likely to get lung cancer.
Radon is a significant risk factor for lung cancer. Because radon gas can’t be seen or smelled, the only way to know whether it’s a problem in your home is to test for it. A Citizen’s Guide to Radon, produced by the EPA, explains how to test your home for radon easily and inexpensively, and what to do if your levels are too high.
Work-related exposure to asbestos and other cancer-causing materials has decreased in recent years, as the government and industry have taken steps to help protect workers. But the dangers are still present, and if you work around these agents, you should be careful to limit your exposure whenever possible.
A healthy diet with lots of fruits and vegetables may also help reduce your risk of lung cancer. Some evidence suggests that a diet high in fruits and vegetables may help protect against lung cancer in both smokers and nonsmokers. But any positive effect of fruits and vegetables on lung cancer risk would be much less than the increased risk from smoking.
Finding lung cancer early
Many people wonder about screening to find lung cancer early, when it’s at a stage that’s likely easier to treat. Screening for lung cancer with CT scans has recently been shown to lower the risk of lung cancer death among heavy smokers in a large study. But these tests carry risks, and for nonsmokers who have a low likelihood of developing lung cancer, the risks of complications from screening are higher than the chances of catching it early, so routine screening isn’t recommended. (Major organizations including the American Cancer Society are now reviewing recent evidence about the benefits and risks of screening in smokers to come up with recommendations for them.)
Advances in treatment
Researchers are learning more and more about what causes cells to become cancerous, and how lung cancer cells differ between nonsmokers and smokers. For example, an article published in Clinical Cancer Research explains that a particular kind of gene mutation is much more common in lung cancer in nonsmokers than smokers.
This mutation activates the gene for epidermal growth factor receptor (EGFR), a protein found on the surface of cells. It normally helps the cells to grow and divide. The mutation causes the gene to be turned on constantly, so the lung cancer cells have too much EGFR, which causes them to grow faster.
Knowing what causes the cell changes has helped researchers develop targeted therapies, drugs that specifically target these mutations. One example is a drug called erlotinib, which has been shown to help keep some lung tumors under control by blocking EGFR from signaling the cell to grow. This drug is much more likely to be helpful in nonsmokers with lung cancer than in smokers.
Authors of the article in Clinical Cancer Research are calling for more research into the genetic makeup of lung cancer in nonsmokers, in order to further define risk factors that contribute to lung cancer in nonsmokers, and to develop new therapies to treat the disease.
Reviewed by: Members of the ACS Medical Content Staff
ACS News Center stories are provided as a source of cancer-related news and are not intended to be used as press releases.
Citations: Lung Cancer Occurrence in Never-Smokers: An Analysis of 13 Cohorts and 22 Cancer Registry Studies. Published in the September 2008 issue of Public Library of Science Medicine (Volume 5, Issue 9). First author: Michael J. Thun, American Cancer Society, Atlanta, Georgia.
Long-Term Ambient Fine Particulate Matter Air Pollution and Lung Cancer in a Large Cohort of Never Smokers. Published on October 6, 2011 in the American Journal of Respiratory and Critical Care Medicine. First author: Michelle C. Turner, University of Ottawa, Ottawa, ON.
Lung Cancer in Never Smokers: Molecular Profiles and Therapeutic Implications. Published online September 14, 2009 in Clinical Cancer Research. First author: Charles M. Rudin, Johns Hopkins University, Baltimore, Maryland.
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