Risk of Lung Cancer in Former Smokers

It's significant, but quitting is always worthwhile

Lung cancer risk drops significantly within five years of quitting, even for people who were once heavy smokers. Nonetheless, the risk of lung cancer is still three-times higher in former heavy smokers compared to people who never smoked at all. Four out of every 10 lung cancers occur in former smokers who quit at least 15 years prior.

That said, the risk does decrease somewhat with time. And without question, becoming a former smoker is one of the best things you can do to reduce your cancer risk and improve your overall health.

This article breaks down lung cancer risk in former smokers compared to people who have never smoked at all. It also explains when and how often to get screened for lung cancer.

Lung Cancer Risk After Quitting

A larger 2018 study also looked at the risk of lung cancer after quitting smoking in almost 4,000 original participants and more than 5,000 of their children.

Roughly 40% of lung cancer cases occurred in people who had quit smoking more than 15 years before their diagnosis.

More specifically, the risk of developing lung cancer after quitting in former heavy smokers was compared with the risk of lifelong non-smokers from five to 25 plus years after quitting. Here's what they found:

Years After Quitting Heavy Smoking  Risk Compared to Lifelong Non-Smokers
 5  12.12 times greater
 5 to 10  11.77 times greater
10 to 15   7.81 times greater
15 to 25   5.88 times greater
Over 25   3.85 times greater

What This Means for Former Smokers

Lung cancer is most treatable in the early stages. When it is discovered early, surgery can offer the chance of a cure.

So, what should you do if you quit smoking 10 years ago, 20 years ago, or more? The answer depends on how much you smoked and when you quit. If you meet the criteria for screening, this is an excellent option.

If you don't, you may wish to talk to your healthcare provider about lung cancer screening anyway, especially if other risk factors are present.

Get Screened

Approximately 70% of new lung cancer cases are already in advances stages by the time they are diagnosed. For those diagnosed with advanced stage lung cancer, the survival rate is about 15%.

Next to smoking cessation, the best method for preventing death due to lung cancer is lung cancer screening via low-dose computed tomography, also known as a CT scan.

In fact, a 2020 study of 15,792 people considered to be "high risk" for lung cancer found that routine screenings reduce the risk of death from lung cancer by 26% for high-risk men, and up to 61% for high-risk women.

The U.S. Preventive Services Task Force recommends using low-dose computerized tomography (CT) to screen for lung cancer in people who:

  • Are between the ages of 50 and 80
  • Have a 20 pack-year history of smoking. (A pack-year is calculated by multiplying the years smoked by the number of packages smoked per day. For example, if you smoked two packs per day for 15 years, that would equal 30 pack-years.)
  • Currently smoke or have quit smoking in the last 15 years
  • Are healthy enough to have surgery if an abnormality is found

The American Cancer Society has similar recommendations, but they don't limit screening to 15 years after quitting.

Be Aware of Symptoms

Having an awareness of the symptoms of lung cancer could mean the difference between finding your disease early or when it has already spread—even if you also get screened, as these tests don't detect all cancers.

Even so, studies have revealed the majority of people are not familiar with the most common symptoms. Part of this is that lung cancer is changing. The types of lung cancer most common in the past are different than the types most common today.

For example, forms of lung cancer such as squamous cell carcinoma of the lungs and small cell lung cancer have become less common. Those cancers tend to grow near the large airways of the lungs and cause symptoms early on, such as a persistent cough or coughing up blood.

Today, lung adenocarcinoma is the most common type of lung cancer. These cancers tend to grow in the outer regions of the lung, rather than near the airways. Symptoms are often a vague sense of shortness of breath that many people disregard as being due to getting older or due to inactivity.

Know Your Risk Factors

In addition to knowing the symptoms of lung cancer, it's important to be aware of your risk factors. These include family history, occupational exposure to chemicals linked to lung cancer, elevated radon levels in the home, and more (in addition to smoking).

Mention any that apply to you to your healthcare provider, as it may factor into their care decisions.

Be Your Own Advocate

If you have any symptoms of lung cancer or any symptoms that don't have an obvious cause, talk to your healthcare provider. If you don't get an adequate explanation for your symptoms, ask for further studies or get a second opinion.

It's not only the general public that is surprised when never-smokers and former smokers who quit long ago develop lung cancer. Many healthcare providers are as well, as they may not have lung cancer high on their radar when evaluating non-smokers.

Among lung cancer survivors, a frequent complaint is that their symptoms weren't addressed thoroughly, or were dismissed since they either never smoked or had kicked the habit.

Remember: Anyone who has lungs can get lung cancer.

Summary

The risk of lung cancer is much higher in current and former smokers compared to people who have never smoked at all. However, quitting does decrease the risk of lung cancer, and the risk continues to decrease with every smoke-free year.

Even if you do develop lung cancer, know that survival rates are better in former smokers than current ones. Whether you are a current smoker or not, getting screened for lung cancer is critical if you are between the ages of 50 to 80, as lung cancer is treatable when caught early.

5 Sources
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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Additional Reading

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."