What Percentage of Smokers Get Lung Cancer?

It's no surprise that smoking leads to an increased risk of cancer, especially lung cancer. However, it can be challenging to grasp just how smoking increases the risk of lung cancer. What percentage of smokers get lung cancer?

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. That said, some people who have never smoked a cigarette can get lung cancer, too. And some people who smoke never go on to develop lung cancer.

In this article, you will learn more about how smoking increases the risk of cancer, how many smokers will go on to develop lung cancer, and how smoking causes cancer. We will also cover whether e-cigarettes are safe, what other cancers smoking can cause, and information about lung cancer screening.

How Many Years of Smoking Causes Lung Cancer?

While it is clear that smoking increases the risk of developing lung cancer significantly, there is no clear-cut formula that says that if a person smokes for a specific length of time, they will indeed develop cancer. Up to 20% of people who develop lung cancer have never smoked a single cigarette in their life. Others might smoke for decades and die of something other than lung cancer.

That said, research has tried to quantify the risk of lung cancer in those who smoke. Here are some considerations:

  • Those who smoke are 15-30 times more likely to develop lung cancer than nonsmokers.
  • The earlier in life you begin smoking, the higher your risk of developing lung cancer.
  • The number of pack-years someone smokes is a factor. 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.

What Is the Life Expectancy of Smokers?

The life expectancy of smokers can vary widely depending on factors like how long the person has been a smoker, how much they smoke, and whether they ever quit. According to the CDC, people who quit smoking can add as many as 10 years to their life expectancy.

What Percentage of Smokers Get Lung Cancer?

A study published in Preventive Medicine Report aimed to assess these risks over 18 years, 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 as follows:

 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%

Why Do Some Smokers Never Get Lung Cancer?

Not everyone who smokes will develop lung cancer. Some studies put the number of smokers who develop lung cancer at about 15%. Other reasons people get lung cancer, including those who have never smoked, include genetic factors, ethnicity, and sex.

One study showed that among its participants, some of the smokers with the greatest number of pack years who had not developed lung cancer seemed to have an increased capacity to repair DNA damage caused by smoking and to suppress further accumulation of mutations. More research needs to be performed to understand how to quantify that for the purposes of lung cancer screening.

Some smokers who might have gone on to develop lung cancer could have a different cancer or illness first and die of that cause before lung cancer develops.

How Does Smoking Cause Cancer?

Many chemicals in cigarettes are known to cause cancer, including formaldehyde, arsenic, and benzene. These chemicals can cause cancer in two ways. First, they can weaken your immune system, making your body less able to kill cancer cells.

These chemicals can also change a cell's DNA, making it more likely to abnormally replicate, leading to cancer.

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.

What Other Cancers Can Smoking Cause?

Smoking can increase the risk of cancer. Because smoking involves inhaling chemicals through your mouth and respiratory tract, common cancers caused by smoking include those areas of the body, and include:

  • Mouth
  • Throat
  • Larynx
  • Trachea
  • Esophagus

Other cancers smoking can lead to include stomach, bladder, colon and rectum, liver, and pancreas, in addition to acute myeloid leukemia.

Are E-Cigarettes Safe?

There has been some speculation that using e-cigarettes, also known as vaping, is less harmful than smoking cigarettes. The truth is we don't know yet. E-cigarettes are relatively new, with the first ones developed in 2003. Early assumptions were that, compared to smoking cigarettes, e-cigarettes might reduce harm even though they still contain nicotine, the addictive substance in cigarettes, because they did not contain some of the cancer-causing agents found in cigarettes.

However, e-cigarettes contain other chemicals, and research is still determining how safe these chemicals are. The liquid contained in e-cigarettes is inhaled into the lungs as an aerosol. The chemicals inhaled include known carcinogenic chemicals like formaldehyde, acetaldehyde, and acrolein, among others.

Because the use of e-cigarettes is relatively recent, not enough time has passed to collect data to analyze how they can impact health.

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 ten 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 few effective lung cancer screening tests. People had to rely on identifying the early symptoms to spot 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 awareness of symptoms 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 significantly. 

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

The American Cancer Society has similar recommendations, except they don't limit screening to those who have quit in the past 15 years. They recommend continuing screening as long as a person doesn't have a health condition that limits their life expectancy or ability to get treatment if cancer is found.

Researchers performed a study that used patients' electronic health records and machine learning to indicate to clinicians which patients might benefit from lung cancer screening. This type of automation might make it easier to determine who should be screened for lung cancer in the future.

Others 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 healthcare provider.

Summary

Smoking is a major risk factor for developing lung cancer. That said, it is difficult to determine exactly which smokers will go on to develop lung cancer. And smoking also increases the risk of other cancers.

While e-cigarettes have previously been considered a safer alternative to smoking, the truth is that e-cigarettes contain some of the same carcinogenic compounds as cigarettes, and there has not been been enough data to determine how risky they are compared to cigarettes.

Screening for lung cancer is one of the best tools to reducing the incidence of death from lung cancer. If you are concerned about your lung cancer risk, speak to a healthcare provider to see if screening is appropriate for you.

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Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Lynne Eldridge, MD
 Lynne Eldrige, MD, is a lung cancer physician, patient advocate, and award-winning author of "Avoiding Cancer One Day at a Time."