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Lung Cancer in Non-Smokers

How is it Different?

By

Updated July 14, 2014

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

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Lung cancer in non-smokers is more common than many people realize. In fact, lung cancer in never-smokers is now considered the 6th most common cause of cancer deaths in the United States.

Though we lump smokers and non-smokers together when discussing lung cancer, lung cancer in non-smokers is a different disease in many ways. What are some of these differences?

Statistics

Overall, 10-15% of lung cancers occur in non-smokers. (Another 50% occur in former smokers.)

Two-thirds of the non-smokers who get lung cancer are women, and 20% of lung cancers in women occur in individuals who have never smoked. This percentage is significantly higher in Asian women.

Causes of Lung Cancer in Non-Smokers

Some of the non-tobacco related causes of lung cancer include:
  • Radon – Exposure to radon gas in our homes is the leading cause of lung cancer in non-smokers.
  • Secondhand smoke - Secondhand smoke is responsible for roughly 3,000 lung cancer deaths yearly in the U.S.
  • Asbestos exposure – Exposure to asbestos on the job is an important cause of mesothelioma, a cancer of the lung lining.
  • Aerosolized oils caused by cooking – Fumes from wok cooking are considered an important cause of lung cancer in women in Asian countries.
  • Other environmental exposures
  • Other occupational exposures
  • Genetic predisposition - Individuals with a family history of lung cancer are more likely to develop lung cancer themselves.
  • Human papillomavirus (HPV) - HPV has been found in lung cancer cells, but whether this indicates it is a cause of lung cancer is still unknown.

Types of Lung Cancer in Non-Smokers

While over half of lung cancers in smokers are classified as squamous cell lung cancers (a type of non-small cell lung cancer), the majority of lung cancers in non-smokers are adenocarcinomas (another type of non-small cell lung cancer).

Squamous cell lung cancers tend to grow near the airways and cause symptoms early on, such as coughing or coughing up blood (hemoptysis).

Adenocarcinomas often grow in the outer regions of the lungs and can be present for a long time before symptoms occur. Symptoms such as shortness of breath, fatigue, or symptoms due to spread of the cancer to other regions of the body (such as bone pain) may be more common.

Bronchoalveolar carcinoma (BAC) is another form of lung cancer that is more common in non-smokers, especially young female non-smokers. For unknown reasons, the incidence of BAC appears to be increasing worldwide.

Biology of Lung Cancer in Non-Smokers

Lung cancer in non-smokers is different than lung cancer in smokers on a genetic, cellular, and molecular level. This means that the changes in cells that make them lung cancer cells are different at all levels, from the genetic blueprint that tells cells when to divide and grow, to the way that the cells function and communicate with other cells. Currently, lung cancer in smokers and non-smokers is treated similarly. As we learn more about the differences between cancer in smokers and non-smokers, this could change. Some studies suggest that individuals who have never smoked respond better to chemotherapy. Some genetic mutations in cancer cells are more common in those who have never smoked, and thus targeted therapies aimed at these mutations may work better in never-smokers.

Prognosis

Lung cancer in non-smokers is often diagnosed at a late stage, being first attributed to a respiratory infection or even allergies. Still, some (but not all) studies suggest that overall survival is better in non-smokers. This difference is most apparent for those who are diagnosed at an early stage of the disease. Female non-smokers have a better prognosis in general than male non-smokers with lung cancer.

Prevention

Checking your home for radon and avoiding secondhand smoke are the most important things you can do to lower your risk of lung cancer as a non-smoker. Certain dietary practices, as well as moderate amounts of exercise, appear to lower risk as well.

Future Directions in Research

Research is currently in progress to figure out ways to detect lung cancer in non-smokers at an earlier stage. In the future, doctors may be able to test for biomarkers, substances in the blood associated with cancer, to find these cancers in non-smokers at the earliest, most treatable stages.

Support

Due to the stigma of lung cancer, non-smokers with lung cancer frequently comment that they feel less support than people with other forms of cancer. Insensitive comments, such as, “I didn’t know you were a closet smoker,” can be hurtful at best and harmful at worst, when individuals feel ashamed to share their struggle with others due to the stigma. Both smokers and non-smokers with lung cancer need our unconditional caring and support.

Sources:

Bryant, A. and R. Cerfolio. Differences in epidemiology, histology, and survival between cigarette smokers and never-smokers who develop non-small cell lung cancer. Chest. 2007. 132(1):185-92.

Couraud, S. et al. Lung cancer in never smokers - A review. European Journal of Cancer. 2012 Mar 28. (Epub ahead of print).

National Institute of Health. NIH News. New Early Detection Studies of Lung Cancer in Non-Smokers Launched Today. 05/04/09. http://www.nih.gov/news/health/may2009/nci-04.htm

Rudin, C. et al. Lung cancer in never smokers: molecular profiles and therapeutic implications. Clinical Cancer Research. 2009. 15(18):5646-61.

Samet, J. et al. Lung cancer in never smokers: clinical epidemiology and environmental risk factors. Clinical Cancer Research. 2009. 15(18):5626-45,

Scagliotti, G. et al. Nonsmall cell lung cancer in never smokers. Current Opinion in Oncology. 2009. 21(2):99-104.

Subramanian, J. and R. Govindan. Molecular genetics of lung cancer in people who have never smoked. Lancet Oncology. 2008. 9(7):676-82.

Subramanian, J. et al. Presentation and stage-specific outcomes of lifelong never-smokers with non-small cell lung cancer (NSCLC).. Journal of Thoracic Oncology. 2007. 2(9):827-30.

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