Risk of Lung Cancer in Former Smokers

Former Smokers at Risk for Lung Cancer Decades Later

The risk of lung cancer in former smokers is significant. In fact, there are more former smokers than current smokers diagnosed with the disease each year, and the risk remains significantly elevated even 25 years after quitting. That said, the risk decreases with time and it's never too late to quit. Let's look at the risk of lung cancer after quitting smoking, whether it has been 5 years, 10 years, 15 years, 20 years, or more than 25 years, and what you need to know in order to catch it as early as possible if it occurs.

Lung Cancer Risk in Former Smokers

Many people are surprised to hear a true statistic about lung cancer: the majority of people who develop lung cancer in 2019 are non-smokers. Some people have never smoked (and at least 20 percent of women who develop lung cancer are never smokers), but the majority of people diagnosed today are former smokers.

Lung cancer occurs more often in people who've already kicked the habit, and that act of courage may have occurred well in the past.

Statistics on Former Smokers and Lung Cancer

It's pretty clear that former smokers are at risk of developing lung cancer, but how great is that risk? How quickly does it decrease after you quit? Once you've stopped, is your risk more like someone who continues to smoke, or someone who has never smoked?

Unfortunately, despite many studies on smoking and cancer we don't have many that address this as a function of risk over the duration of quitting. Yet a few studies that look at the problem in different ways give us a fairly good idea of risk over the long run.

Risk of Lung Cancer After Each Decade of Quitting

Researchers looked at over 600 people who were referred for lung cancer surgery and who were asked the question; "Did you smoke, and if so, when did you quit?"

Of these patients 77 percent had a history of smoking in the past, but only 11 percent were current smokers. Note, this is common. The "average" patient had quit smoking 18 years before the diagnosis of lung cancer. The former smokers were broken down further by how long they had been "smoking abstinent":

  • 14 percent had been smoke-free for less than a year
  • 27 percent were smoke-free for 1 to 10 years
  • 21 percent were smoke-free for 10 to 20 years
  • 16 percent were smoke-free for 20 to 30 years
  • 11 percent were smoke-free for 30 to 40 years
  • 10 percent were smoke-free for 40 to 50 years

The conclusion was that the majority of patients in this group had been smoke-free for more than a decade prior to their diagnosis of lung cancer. It is important to note that this was a group that was referred for surgical treatment of lung cancer, and as such, were likely in the earlier stages of the disease.

Risk of Lung Cancer up to 25 Years After Quitting

A larger 2018 study (part of the Framingham Heart Study) also looked at the risk of lung cancer after quitting smoking in almost 4,000 original participants and over 5,000 offspring. The results were alarming considering that lung cancer screening is now approved for people who smoke or have quit in the past 15 years.

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

In this study, the risk of developing lung cancer after quitting in former heavy smokers was compared with the risk in lifelong non-smokers from 5 years to 25 plus years after quitting. The risk was as follows:

  • 5 years after quitting: 12.12 times that of a never smoker
  • 5 to 10 years after quitting: 11.77 times
  • 10 to 15 years after quitting: 7.81 times
  • 15 to 25 years after quitting: 5.88
  • Over 25 years since quitting: 3.85

It's noteworthy that the risk is almost four times higher than a never smoker even 25 years after smoking, an interval of time that is a decade beyond the current recommendations for lung cancer screening. (And even more concerning as a 2019 study found that lung cancer screening may even play a role for never smokers.)

Importance of Alerting Former Smokers to This Risk

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

So what does this mean for you personally? What should you do if you quit smoking 10 years ago, 20 years ago, or more?

The answer at the current time 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? Some people may wish to talk to their doctors about lung cancer screening even though they do not meet all the criteria, especially if other risk factors are present such as a family history, occupational exposure to chemicals linked to lung cancer, elevated radon levels in the home, and more.

Having an awareness of the symptoms of lung cancer could make the difference between finding your disease early, or finding it when it has already spread. Yet even if you have screening, knowing the symptoms is important as screening does not detect all cancers.

Knowing the symptoms seems easy, right? Unfortunately, recent studies tell us that 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 used to be more 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, and not near the airways. Symptoms are often a vague sense of shortness of breath than many people disregard as being due to getting older or due to inactivity.

Lung Cancer Screening

Lung cancer screening is available for some people, and it's thought that using screening could decrease the death rate from lung cancer by 20 percent in the United States. The current criteria include those who:

  • Smoke or smoked for at least 30 pack years. (A pack year is calculated by multiplying the years smoked by the number of packages smoked per day. For example, if you smoked 2 packs per day for 15 years, that would equal 30 pack years.)
  • Are between the ages of 55 and 80.
  • Continue to smoke or quit smoking in the last 10 years.
  • Are healthy enough to have surgery if an abnormality is found.

Know Your Risk Factors

In addition to knowing the symptoms of lung cancer, it's important to be aware of your risk factors. Some of these may be obvious, but others are less well known. Some people may choose to have lung cancer screening even if they don't meet the smoking criteria.

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 doctor.  If you don't have 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 physicians, as well, don't have lung cancer high on the radar screen in non-smokers. Among lung cancer survivors, a frequent complaint is that their symptoms weren't addressed aggressively enough, or were dismissed since they either never smoked or had kicked the habit.

Unfortunately, the stigma of lung cancer being a smoker's disease is not only hurtful to people living with lung cancer, but it produces a false confidence in those who never smoked or quit. But anyone who has lungs can get lung cancer.

A High Five for Quitting

It can be discouraging to hear about the persistent risk of lung cancer after quitting smoking. It's important to note that the risk does decrease, and unlike lung cancer risk, the risk of heart disease decreases fairly rapidly. Everyone who has the courage to kick the habit deserves our commendation. It makes a difference. And even for those who do develop lung cancer, survival rates are better in those who don't currently smoke.

Lessons From the Risk of Lung Cancer in Former Smokers

Looking at studies of cancer risk after quitting smoking confirms what we already know: most people who develop lung cancer are non-smokers. This is important in many ways.

One, is that it tells us that encouraging smoking cessation isn't enough to eliminate lung cancer deaths. Raising awareness about the risk of smoking is certainly important, but it can also be detrimental when it is the only effort being forth to make a difference with lung cancer.

Research into the causes of lung cancer has lagged behind what would be expected with other cancers, largely due to its being dismissed as being caused by smoking. A quick calculation can drive home this point. In 2019 it's expected that 40,000 people will die from breast cancer. At the same time, it's expected that 21,000 to 27,000 will die from radon-induced lung cancer; a disease that is completely preventable if people would all check their homes for radon levels, and have radon mitigation if needed. If we had a way to inexpensively test for, and eliminate the cause of over 50 percent of breast cancer deaths (eg. 20,000 deaths), most everyone would be very familiar with the process. Yet, not everyone is aware of simply testing their homes for radon.

Perhaps, if lung cancer were given the attention given to breast cancer, we would already have a screening test available for those who quit smoking more than 15 years ago.

A final concern is the stigma. We need to stop asking people with lung cancer if they smoked and leave the assessment of possible causes to epidemiologists. It's time for us to love and care for people with lung cancer in the same way as we care for people with other types of cancer.

Reducing Your Risk of Lung Cancer

While overshadowed by quit smoking campaigns, there are some things people can do to reduce their risk of lung cancer. This includes checking your home for radon, being careful with chemicals used at work to reduce occupational causes of lung cancer, exercising regularly, and eating a healthy diet rich with some of the superfoods that may lower lung cancer risk.

A Word From Verywell

The risk of lung cancer remains elevated for at least 25 years after quitting, though other risks related to smoking decrease more rapidly. Fortunately, lung cancer screening is now available for some people, and it's thought that a simple blood test (cell free DNA) may be a way in the near future to screen anyone for the disease.

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