November 2, 2014 | by Nicole White
The single largest risk factor for lung cancer is smoking, and it contributes to the overwhelming majority of lung cancer cases.
That's old news, of course. What might be news to many people is that, although smoking is a major cause of lung cancer, it's not the only cause. In fact, a growing number of cases are occurring in patients who never smoked and who did not have significant exposure to secondhand smoke.
About 15 percent of lung cancers are diagnosed in people who do not smoke. Further, about 60 percent or more occur in nonsmokers, including people who never smoked and those who quit many years before their diagnosis.
Success in smoking education and cessation efforts means fewer smokers, but as the numbers of smokers developing lung cancer declines, scientists are recognizing how much we have to learn about the causes of this disease.
Other lung cancer risk factors:
Exposure to secondhand smoke: Still related to smoking, yes, but a factor worth considering. With smoking banned in restaurants, planes and many other public spaces, exposure to secondhand smoke is dropping. However, many of us still remember sitting on smoke-filled airplane flights, and in smoky offices, homes and cars heavy with cigarette smoke.
Dan Raz, M.D., co-director of the Lung Cancer and Thoracic Oncology Program at City of Hope, is an investigator in a multicenter study evaluating lung cancer screening with low-dose CT scans for those exposed to secondhand smoke. Researchers, physicians and the public have much more to learn about the risks of secondhand smoke exposure, he says.
Family history: Unlike with some breast cancers and other cancers, scientists have not been able to pin lung cancer to any specific, heritable gene mutations. Lung cancer risk is higher among those whose parents, siblings or children have had lung cancer. What’s still unclear is how much of that is genetic and how much is environmental – as members of the same family are likely to live in the same place and be exposed to the same cancer-causing agents.
Radon: The U.S. Environmental Protection Agency has linked radon to about 20,000 cases of lung cancer each year, making it the second-leading known cause of lung cancer, according to the federal Centers for Disease Control and Prevention (CDC). The invisible, odorless, tasteless gas comes from rocks and dirt and can be trapped in houses and buildings. An estimated one in 15 homes in the U.S. has high radon levels. The EPA offers information on testing and reducing radon levels.
Radiation therapy to the chest: Cancer survivors treated with radiation therapy to their chest have a higher risk of developing lung cancer. (Breast cancer, now lung cancer, survivor Susan shares her story.) Women who were treated with radiation following a mastectomy and those treated for Hodgkin disease are at highest risk, according to the CDC.
Diet and other environmental factors: Some substances are known to be linked with lung cancer, such as asbestos, diesel exhaust and arsenic. The National Cancer Institute lists use of beta carotene supplements as increasing risk, especially in heavy smokers and smokers who have one alcoholic drink a day. Diet and lung cancer is a topic of many studies, but so far, there’s no definitive study on what foods might cause or prevent lung cancer. Though, several studies indicate that people who eat a diet rich and fruits and vegetables are at a lower risk of lung cancer – something that’s true for many cancers.
At the end of the day, quitting cigarettes and other tobacco products remains the best advice for reducing lung cancer risk. In October, the Journal of the American Medical Association published a study estimating that adults in the U.S. suffered from about 14 million major medical conditions attributable to smoking.
But being aware of, and reducing, other risk factors for lung cancer is a smart choice.
Learn more about lung cancer treatment and research at City of Hope.
Learn more about becoming a patient or getting a second opinion at City of Hope by visiting our website or by calling 800-826-HOPE (4673). City of Hope staff will explain what's required for a consult at City of Hope and help you determine, before you come in, whether or not your insurance will pay for the appointment.