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What Percentage of Smokers Get Lung Cancer?

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Updated April 04, 2014

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

Question: What Percentage of Smokers Get Lung Cancer?
Answer:

We know that smoking causes lung cancer, but it’s also clear that some people smoke their whole lives and never develop lung cancer. What percentage of smokers get lung cancer?

Lifetime Risk of Lung Cancer in People Who Smoke

Most statistics look at the overall risk of lung cancer, combining both people who smoke and those who have never smoked. Based on United States statistics, the lifetime risk that an individual (men and women combined) will develop lung cancer is 6.9%, or 1 in 13 people. Clearly this number would be higher for people who smoke and much lower for people who have never smoked.

Studies in other countries have broken down the risk further to differentiate between never smokers, former smokers, and current smokers.

In a 2006 European study, the risk of developing lung cancer was:

  • 0.2% for men who never smoked (0.4% for women)
  • 5.5% for male former smokers (2.6% in women)
  • 15.9% for current male smokers (9.5% for women)
  • 24.4% for male “heavy smokers” defined as smoking more than 5 cigarettes per day (18.5% for women)

An earlier Canadian study quoted the lifetime risk for male smokers at 17.2% (11.6% in women) versus only 1.3% in male non-smokers (1.4% in female non-smokers).

Risk of Lung Cancer Based on Duration of Smoking

The earlier in life you begin smoking, the higher your risk of developing lung cancer. Your risk also depends on the number of “pack-years” you have smoked. A pack-year is a number that is calculated by multiplying the number of years smoked times the number of packs of cigarettes smoked daily.

Quitting Smoking or Cutting Down Lowers the Risk of Lung Cancer

Quitting smoking lowers the risk of lung cancer, but it can take some time before your risk decreases. If you have smoked for more than a short period of time your risk will never reach that of a never smoker, but it is still very worth the effort to quit. Researchers looking at people in Asia and Australia found that people could reduce their risk of developing lung cancer by up to 70% by quitting smoking.

In one estimate, a 68-year-old man who had smoked two packs per day for 50 years (100 pack years) had a 15% risk of developing lung cancer in the next 10 years if he continued to smoke. This risk would drop to 10.8% if he quit smoking.

Does Cutting Down But Not Quitting Help?

The answer is that it may. In one study, it was found that people who smoked more than 15 cigarettes per day could significantly lower their risk if they cut the number of cigarettes they smoked daily in half. Another study was less positive about the cutting down approach, and suggested that quitting altogether was necessary to bring about a significant difference in risk.

Predicting Lung Cancer Risk

While it is impossible to truly predict who will develop lung cancer, Memorial Sloan-Kettering Cancer Center has developed a Lung Cancer Risk Assessment Tool in which you can calculate your average risk of developing lung cancer in the next 10 years, based on your age and how long you had or have smoked.

The tool is designed for people between the ages of 50 and 75, who smoked between 10 and 60 cigarettes daily for a period of 25 and 55 years. It is preceded by a disclaimer that reminds individuals that the tool is only a prediction based on statistics, and does not mean someone will or will not develop lung cancer.

Smoking after a Diagnosis of Lung Cancer

Even if you have already been diagnosed with lung cancer, quitting is worth the effort. Quitting smoking if you have lung cancer may improve your response to treatment, and possibly even, survival.

Smoking Risk Goes Beyond Lung Cancer

As a final note it is important to point out that smoking is responsible for many conditions in addition to lung cancer.

Further Reading:

Sources:

American Cancer Society. Lifetime Risk of Developing or Dying From Cancer. Updated 08/08/10. http://www.cancer.org/Cancer/CancerBasics/lifetime-probability-of-developing-or-dying-from-cancer

Bach, P. et al. Variations in Lung Cancer Risk Among Smokers. Journal of the National Cancer Institute. 2003. 95(6):470-478.

Brennan, P. et al. High Cumulative Risk of Lung Cancer Death among Smokers and Nonsmokers in Central and Eastern Europe. American Journal of Epidemiology. 2006. 164(12):1233-1241.

Centers for Disease Control and Prevention. Lung Cancer. Risk Factors. Smoking and Secondhand Smoke. Updated 09/15/10. http://www.cdc.gov/cancer/lung/basic_info/risk_factors.htm

Godtfredsen, N. et al. Effect of Smoking Reduction on Lung Cancer Risk. Journal of the American Medical Association. 2005. 294(12):1505-1510.

Huxley, R. et al. Impact of Smoking and Smoking Cessation on Lung Cancer Mortality in the Asia-Pacific Region. American Journal of Epidemiology. 2007. 165(111):1280-1286

National Cancer Institute. Harms of Smoking and Health Benefits of Quitting. Updated 10/28/10. http://www.cancer.gov/cancertopics/factsheet/Tobacco/cessation

National Cancer Institute. Surveillance Epidemiology End Results. SEER Stat Fact Sheets: Lung and Bronchus. Accessed 02/23/11. http://seer.cancer.gov/statfacts/html/lungb.html#risk

Villeneuve, P. and U. Mao. Lifetime probability of developing lung cancer, by smoking status, Canada. Canadian Journal of Public Health. 1994. 85(6):385-8.

Zhang, B. et al. Smoking cessation and lung cancer mortality in a cohort of middle-aged Canadian women. Annals of Epidemiology. 2005. 15(4):302-9.

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