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Why Lung Cancer Strikes Nonsmokers

Article date: October 28, 2013

By Stacy Simon

Most people know that smoking causes cancer, but may not realize how many nonsmokers get lung cancer, too. Every year, about 16,000 to 24,000 Americans die of lung cancer, even though they have never smoked. In fact, if lung cancer in nonsmokers had its own separate category, it would rank among the top 10 fatal cancers in the United States.

Unfortunately, a perception that patients contributed to their own illness by smoking harms both smokers and nonsmokers with lung cancer. Lung cancer expert Joan H. Schiller, MD, of the University of Texas Southwestern Medical Center in Dallas, co-authored a study measuring public attitudes about lung cancer. The study found that 70% of participants had a negative attitude about lung cancer. By comparison, only 22% had a negative attitude about breast cancer.

Even so, researchers have made a lot of progress over the past decade in understanding some of the causes of lung cancer in nonsmokers and how to treat it.

  • Radon gas. 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. 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, as well as what to do if your levels are too high.
  • Secondhand smoke. Each year, an estimated 3,400 nonsmoking adults die of lung cancer as a result of breathing secondhand smoke. Laws that ban smoking in public places have helped to reduce this danger. The American Cancer Society Cancer Action Network (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.
  • Cancer-causing agents at work. For some people, the workplace is a source of exposure to carcinogens like asbestos and diesel exhaust. Work-related exposure to such 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.
  • Air pollution. It’s long been known that both indoor and outdoor air pollution contribute to lung cancer. In October 2013, the International Agency for Research on Cancer (IARC), part of the World Health Organization, classified outdoor air pollution as a cancer-causing agent. The IARC evaluated more than 1,000 studies and concluded that increased exposure to outdoor air pollution increases the risk of lung cancer.
  • Gene mutations. 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 a gene that normally helps cells grow and divide. The mutation causes the gene to be turned on constantly, so the lung cancer cells grow faster. Knowing what causes the cell changes has helped researchers develop targeted therapies, drugs that specifically target these types of mutations.

Lifestyle changes to lower 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.

Testing your home for radon, avoiding secondhand smoke, and limiting exposures at work can help you avoid the leading causes of lung cancer in nonsmokers.

A healthy diet with lots of fruits and vegetables may also help reduce your risk. 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

The idea of screening for lung cancer with a low-dose computed tomography (CT) scan is appealing, because it has the potential of finding the cancer earlier, when it’s likely to be easier to treat. Lung cancer symptoms don’t usually appear until the cancer is already advanced and not able to be cured. Screening is done in people who do not have any symptoms of cancer. But screening carries risks that may outweigh the benefits except in people at higher than average risk for lung cancer, often heavy smokers. Age is also a risk factor.

One drawback of a low-dose CT scan is that it finds a lot of abnormalities that turn out not to be cancer but that still need to be assessed to be sure. This may lead to additional scans or even more-invasive tests such as needle biopsies or even surgery to remove a portion of lung in some people. A small number of people who do not have cancer or have very early stage cancer have died from these tests. There is also a risk that comes with increased exposure to radiation.

Because of these risks, the American Cancer Society recommends doctors discuss lung cancer screening with people who meet certain criteria that put them at high risk for developing the disease. These high-risk patients must be aged 55 to 74 years and in fairly good health, have a smoking history equivalent to a pack a day for 30 years, and currently smoke or have quit within the past 15 years.

If people decide to be screened, the recommendation specifies that testing should take place at a facility with experience in lung cancer screening. And it emphasizes that screening is not a substitute for quitting smoking. The most effective way to lower lung cancer risk is to stay away from tobacco.

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. For reprint requests, please contact permissionrequest@cancer.org.

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