What Percentage of Smokers Get Lung Cancer?

Most statistics look at the overall risk of lung cancer, combining people who smoke with those who have never smoked.

According to data from the National Cancer Institute (NCI) covering the years 2015 to 2017, the lifetime risk of developing lung cancer in the United States among all groups is 6.3% (or roughly one out of every 15 people).

This number would be higher for those who have smoked and lower for those who have never smoked. Cigarette smoking is responsible for 80% to 90% of all lung cancer cases, making it the top cause of the disease. And those who smoke are as much as 30 times more likely to get lung cancer than those who don't.

However, until recently, those factors were inadequately researched and often failed to address factors like the dynamics of risk among male and female smokers.

Lifetime Risk by Smoking Status

A 2018 study published in Preventive Medicine Report aimed to assess these risks over an 18-year period, categorizing male and female smokers as "never smokers," "former smokers," or "current smokers." A total of 9,623 lung cancer cases from 1995 to 2013 were included in the evaluation.

Based on the findings, the researchers estimated that lifetime risk of lung cancer by smoking status in males and females is:

 Smoking Status Male Lifetime Risk  Female Lifetime Risk
Never smoker  1.8% 1.3%
Former smokers   7.2% 5.8%
Current smokers  14.8%  11.2%

The researchers reported the lifetime risk of lung cancer in males dropped from 7.1% to 6.7% during the 18-year study period but increased in females from 2.5% to 4.1%, reflecting the increased use of cigarettes among females.

But these numbers don't differentiate risk by how much a person smokes and what happens if they quit. As such, the picture they paint about lifetime risk of lung cancer is incomplete.

Lung Cancer Risk in Heavy Smokers

It appears 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 calculated by multiplying the number of years you smoked times the number of packs of cigarettes smoked daily.

Quitting cigarettes lowers the risk of lung cancer, but it can take some time before that risk decreases. Even if you smoked a few cigarettes a day or only occasionally, your risk will never reach that of a never smoker.

A 2018 study in the Journal of the National Cancer Institute aimed to evaluate these dynamics by looking at lung cancer statistics from 1954 until 2013. Researchers found heavy smokers (those with more than 21.3 pack-years) were able to reduce their risk upon quitting cigarettes and that the benefits increased with each advancing year.

By keeping off cigarettes for five years, heavy smokers reduced their risk of lung cancer by 39.1% compared to heavy smokers who did not quit. By 10 years, the risk was halved.

Still, while quitting is always worthwhile, it can't entirely erase a person's history of smoking.

Even if a heavy smoker were to have quit cigarettes 25 years ago, their risk of cancer today would still be three times greater than that of a person who never smoked. No less than 40.8% of all lung cancers occur 15 years after a person has stopped smoking.

Causes of Cancer Deaths

Smoking is the leading cause of cancer-related deaths for males and females in the United States. In fact, one out of four cancer deaths is due to lung cancer, killing more people than breast cancer, prostate cancer, and colon cancer combined.

It is thought that at least 90% of lung cancer deaths can be attributed to smoking.

There are many chemicals in cigarettes that are known to cause cancer, including formaldehyde, arsenic, and benzene. These not only contribute to the development of lung cancer but other cancers as well, including cancers of the mouth, throat, stomach, colon, rectum, kidney, bladder, cervix, and blood (most commonly acute myeloid leukemia).

It's not just smoking that's the problem. It is thought that roughly 7,300 Americans die from lung cancer each year due to secondhand smoke.

Predicting Lung Cancer Risk

While it is impossible to predict who will or will not develop lung cancer, Memorial Sloan-Kettering Cancer Center has developed a Lung Cancer Screening Decision Tool that certain people can use to calculate their risk of developing lung cancer in the next 10 years based on age and how long they've smoked.

The tool is designed for people ages 50 to 75 who have smoked between 10 and 60 cigarettes daily for a period of 25 to 55 years. It reminds you that the results are only a prediction and do not mean that you definitely will or will not develop lung cancer.

Lung Cancer Screening

In the past, there were not many effective screening tests for lung cancer. People had to rely on the identification of the early symptoms in the hope of spotting the disease in the initial and most treatable stages.

However, since nearly half of people with lung cancer are diagnosed in the advanced stages, general knowledge may not be enough to keep you safe.

For people who are at an increased risk of lung cancer, advanced computed tomography (CT) screening can improve the chances of early detection and, when used appropriately, reduce the risk of mortality by 20%. 

According to the U.S. Preventive Services Task Force, people who should have yearly CT screenings for lung cancer are those who:

  • Are between the ages of 50 and 80
  • Have a 20 pack-year history of smoking
  • Currently smoke or have quit in the past 15 years
  • Are in reasonable physical condition such that surgery can be performed if a tumor is found

There are others who may benefit from screening as well. For example, anyone exposed to cancer-causing substances in the workplace, such as radon or aerosolized benzene, may reasonably request CT screening.

If you feel that you are at an increased risk of cancer and require screening, talk to your doctor.

A Word From Verywell

If you smoke or have smoked in the past, don't assume it's too late to act. Instead of focusing on your risk of cancer, consider how quitting can slash your risk by half in 10 years.

There are numerous smoking cessation aids that can increase your chances of success, including nicotine replacement tools and medications like Chantix (varenicline). Many of these aids are listed as Essential Health Benefits (EHBs) under the Affordable Care Act and are provided free of charge by your insurer or health provider, even for multiple quit attempts.

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Article Sources
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