If you never smoked, lung cancer may not be on your radar as a high-risk health concern. Yet roughly one in five people who develop lung cancer are lifelong nonsmokers. What’s more, some recent studies suggest the incidence of these potentially deadly malignancies in “never-smokers” may be on the rise-especially in people ages 65 and older. Why lung cancer might be striking more people who avoid tobacco is unclear, but some doctors are calling for greater awareness of the threat. An editorial in the Journal of the Royal Society of Medicine in April 2019 noted that “lung cancer in people who have never smoked is under-recognised, rather than uncommon.”
Worldwide, 15 to 20 percent of males and more than half of females who develop lung cancer are never-smokers. The U.S. Centers for Disease Control and Prevention (CDC) defines a never-smoker as a person who has never smoked or smoked fewer than 100 cigarettes in their lifetime.
Some research suggests that lung cancer in never-smokers is increasing. A study published in the Journal of the National Cancer Institute in January 2017 found that the proportion of never-smokers treated for non-small cell lung cancer at three hospitals in Texas and Tennessee rose from 8 percent in the early 1990s to 14.9 percent by 2013.
Non-small cell lung cancer is one of the two major types of lung cancer. The other is small cell lung cancer, the most aggressive form. The two types differ in the way they grow and spread. Non-small cell lung cancer accounts for about 80 to 85 percent of all lung cancers and is the most common form in never-smokers. Small-cell lung cancer accounts for about 10 to 15 percent of lung cancers and is almost exclusively seen in heavy smokers.
Both forms have several subtypes. Adenocarcinoma, the most common subtype of non-small cell lung cancer, is diagnosed most often in nonsmokers, light smokers and former smokers. It tends to develop in the lungs’ outer regions, and symptoms take longer to appear compared with those of small cell lung cancer subtypes.
More than secondhand smoke
Scientists have known since the 1980s that secondhand smoke is a risk factor for lung cancer in never-smokers. Secondhand smoke is made up of smoke from burning cigarettes and other tobacco products.
Other factors have been associated with lung cancer among never-smokers, although their role is not entirely clear to scientists. The most common factors associated with lung cancer include:
- Radon. This colorless, odorless gas is produced by the natural breakdown of uranium in rock, soil, and groundwater and can become concentrated in buildings. Testing is the only way to know whether your home has high radon levels. Visit www.epa.gov/radon or call the National Radon Hotline at 1-800-55RADON to learn how to test your home.
- Workplace exposure. People whose jobs expose them to substances such as diesel exhaust and hazardous chemicals have an increased risk for lung cancer. If you work in an industry where you inhale lung irritants, insist on proper ventilation, try to limit your exposure, and wear appropriate protective gear. If you think your job exposes you to carcinogens, check government regulations for your workplace. You can download a guide to occupational chemical hazards at cdc.gov/niosh/npg.
- Genes. Inheriting or acquiring certain genetic mutations makes people vulnerable to lung cancer, even if they don’t smoke.
- Air pollution. Outdoor air pollution accounts for 29 percent of all deaths and disease from lung cancer worldwide, according to the World Health Organization. Lung cancer from pollution is more predominant in many other countries than in the United States because of U.S. environmental protection policies.
Risk factors and symptoms
The risk for lung cancer among never-smokers rises sharply at around age 60. Female never-smokers are more likely to develop lung cancer than their male counterparts, though the latter are more likely to die of the disease. Race plays a role, too; for reasons that aren’t clear, 60 to 80 percent of Asian women diagnosed with lung cancer are never-smokers.
Lung cancer tends to be diagnosed at advanced stages in never-smokers. One reason may be that adenocarcinomas grow or spread before symptoms develop. Another reason may be that never-smokers don’t believe they’re at risk and aren’t as aware of lung cancer symptoms, so diagnosis is delayed. While most symptoms and signs are common to less serious illnesses, nonsmokers shouldn’t dismiss them. They include chronic cough, bloody sputum, shortness of breath, wheezing, chest pain, hoarseness, and headache.
Despite the oft-delayed diagnoses, some observational studies suggest that never-smokers have a better treatment response and prognosis than smokers, although other studies haven’t confirmed this. One reason could be that the type of lung cancer never-smokers develop responds better to new-generation cancer therapies that target certain gene mutations.