Lung cancer

Risk factors

• Smoking: Smoking is the greatest known risk factor for lung cancer and is estimated to be responsible for approximately 90% of lung cancer in men and 85% in women. Lung cancer risk attributable to tobacco smoking is strongly affected by the duration of smoking, and declines with increasing time from cessation. Thus, the estimated lifetime risk of lung cancer among former smokers ranges from approximately 6% in smokers who give up at the age of 50, to 10% for smokers who give up at age 60, compared to 15% for lifelong smokers and approximately 1% in never-smokers.
• Secondary smoke: Secondary smoke is estimated to cause approximately 3,000 lung cancer deaths per year among non-smokers and contributes to more than 35,000 deaths linked to cardiovascular disease.
• Genetics: Regardless of exposure to tobacco smoke, there are important individual differences in the risk of developing lung cancer, some of which are attributable to genetic factors. Thus, for example, even though smoking is the primary cause of lung cancer, only about 15% of lifelong smokers will actually develop this disease. Genetic factors may influence who end up developing the disease. The role of genetics is further demonstrated by the fact that close relatives of lung cancer patients have an approximately two-fold greater risk of developing the disease compared to the general population.
• Environmental pollutants: Exposure to a variety of environmental factors or industrial substances has been associated with increased risk of lung cancer. These include asbestos, radon and arsenic. Certain lung diseases can also increase the risk for lung cancer. However, these factors combined still contribute much less to the disease risk than tobacco smoking.

Prevention and treatment

The best way to avoid lung cancer by far is not to smoke and to avoid second-hand smoke and other environmental factors that may increase the risk of the disease.

There is some evidence that suggests that a diet rich in fruit may have protective effect against lung cancer. Furthermore, smokers may benefit from eating vegetables. Several large studies have been conducted in order to test if intake of vitamins or other supplements might protect against lung cancer. To date, there is limited evidence that this might be the case. Highly publicized studies of beta-carotene and vitamin A supplementation in smokers actually showed an increase in lung cancers in the supplementation groups. In another study of over 75,000 individuals it was shown that the long-term use of supplemental multivitamins, such as vitamin C, vitamin E, and folate did not reduce the risk of lung cancer. On the contrary, the results of the study indicated that high doses of vitamin E might even increase the risk of lung cancer.

Individuals who are identified as being at high risk for lung cancer may be referred to have chest X-rays or sputum cytology examination. In addition, a spiral CT scan is a newly-developed procedure for lung cancer screening. Numerous lung cancer screening trials are currently taking place but presently, the U.S. Preventive Services Task Force (USPSTF) concludes that evidence is insufficient to recommend for or against screening asymptomatic persons for lung cancer.

The outcome of lung cancer depends on the tumor type, how advanced the disease is when it is diagnosed, and the general health of the person diagnosed. Overall, lung cancer is one of the most difficult cancers to treat. If the disease is diagnosed early, then more treatment options are available and prognosis is better. Treatment options include surgery, radiation, chemotherapy, or a combination of these.

More information

You can find out more information about lung cancer and smoking by talking to your doctor and visiting these Web sites:

• Centers for Disease Control and Prevention on Smoking and Nicotine Dependence
• Lung Cancer.org, A Program of Cancer Care
• National Cancer Institute on Lung Cancer

This content was last reviewed on February 11, 2010.