What Percentage of Smokers Get Lung Cancer?

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x-ray of smoke in lungs
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We know that smoking causes lung cancer, but it’s also clear that some people smoke their whole lives and never develop lung cancer. So, what percentage of smokers actually get lung cancer?

Overview

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 a man will develop lung cancer is 7.62 percent, or one in 13 people.

The lifetime risk of a man dying from lung cancer is 6.26 percent, or one in 16.

For women, ​the lifetime risk of developing lung cancer is 6.61 percent, or one in 15. The lifetime risk of a a woman dying from lung cancer is 4.99 percent, or one in 20. Clearly, these numbers 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 percent for men who never smoked; 0.4 percent for women
  • 5.5 percent of male former smokers; 2.6 percent in women
  • 15.9 percent of current male smokers; 9.5 percent for women
  • 24.4 percent for male “heavy smokers” defined as smoking more than five cigarettes per day; 18.5 percent for women

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

Risk

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 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 percent 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 percent risk of developing lung cancer in the next 10 years if he continued to smoke. This risk would drop to 10.8 percent if he quit smoking.

You may also be wondering how cutting down but not quitting impacts risk? 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

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.

Diagnosis

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.

It is also important to point out that smoking is responsible for many conditions in addition to lung cancer.

Find out more:

Screening

Until recently, there had not been an effective screening test. People needed to rely on an awareness of the early symptoms of lung cancer.

Since nearly half of people are diagnosed when their lung cancer is already stage 4, a knowledge of symptoms alone isn't enough. Thankfully—for some people at least—CT lung cancer screening has now been approved and, when used according to guidelines, may decrease the mortality from lung cancer by 20 percent in the United States.  

People eligible for screening include those who:

  • Are between the ages of 55 and 80
  • Have a 30 pack-year history of smoking
  • Continue to smoke or quit smoking in the past 15 years

There are other people who may wish to be screened as well. For example, those who have been exposed to cancer-causing substances in the work place. If you feel you may be at risk, talk to your doctor. Even if you smoked, it's not too late to do other things to lower your risk of developing lung cancer.

Sources:

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. 5/06/14.

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. 12/03/14.

National Cancer Institute. Surveillance Epidemiology End Results. SEER Stat Fact Sheets: Lung and Bronchus. 2/23/11.

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