Non-smokers are at increasing risk for lung cancer

Soha Mahmoud, for MDLinx | June 10, 2019

The prevalence of lung cancer in people who have never smoked is more common than many realize—and it’s on the rise, despite declining rates of smoking. The relative proportion, absolute number, and rates of lung cancers are all increasing in never-smokers. However, because lung cancer is traditionally associated with smoking, the risk in never-smokers remains largely underrecognized and underdiagnosed. In fact, among the number of Americans to be newly diagnosed with lung cancer this year, up to 15% have never smoked.


Worker smoking near factory

Second-hand smoke, air pollution, radon, and other causes are increasing the numbers of non-smokers diagnosed with lung cancer.

Now, respiratory medicine and public health experts are calling for enhanced awareness, among both clinicians and the general public, of lung cancer in lifetime never-smokers. In a report recently published in the Journal of Royal Society of Medicine, these authors pointed out that most never-smokers don’t believe they’re at risk for lung cancer.

“For too long, having lung cancer has only been thought of as a smoking related disease. This remains an important association but, as this this work shows, the scale of the challenge means there is a need to raise awareness with clinicians and policy makers of the other risk factors including indoor and outdoor air pollution,” noted lead author Paul Cosford, MB, ChB, FFPHM, director for health protection & medical director, Public Health England, London, United Kingdom.

Not enough federal funding

According to the CDC, cigarette smoking is linked to about 80% to 90% of lung cancer deaths in the United States, and smokers are 15-30 times more likely to either develop lung cancer or die from lung cancer vs non-smokers. However, while it may seem that the odds are in the favor of non-smokers, the reality is a bit different.

Of the 228,000 people in the United States who will receive lung cancer diagnoses this year, 60% to 65% will be never-smokers or former smokers, with never-smokers making up 10% to 15% of all new lung cancer cases. Although lung cancer is the leading cause of cancer death— accounting for 24% of all cancer deaths and claiming more lives than colorectal, breast, and prostate cancers combined—only 6% of federal funding is allocated to lung cancer research.

In fact, only $2,488 in federal funding dollars are spent per life lost to lung cancer (n=142,670), compared with $16,777 per life lost to breast cancer (n=42,260).

With lung cancer killing about 1.5 times as many women as breast cancer, Dr. Cosford and colleagues delved deeper into this discrepancy. They found that, historically and medically, messaging on smoking and its direct impact on lung cancer has, in part, unintentionally caused lung cancer to receive much less attention than breast, prostate, and ovarian cancers.

“The stigma of smoking has been the major factor behind the lack of interest in, knowledge of, and research into lung cancer. Therefore, in many ways, never-smokers who develop lung cancer are, as a result, disadvantaged,” remarked co-author Michael D. Peake, MB, ChB, FRCP, clinical director, Centre for Cancer Outcomes, University College London Hospitals Cancer Collaborative, London, United Kingdom.

The current under-recognition of lung cancer in non-smokers poses a challenge for general practitioners who strive to provide early diagnosis and quality care while avoiding excess workup on patients. In attempting to do so, it is important to raise awareness of other risk factors that are linked to the development of lung cancer, aside from smoking.

Risk factors other than smoking

Second-hand smoke still represents a major contributing factor to the development of lung cancer in non-smokers. The CDC equates the impact of passive secondhand smoke to active smoking. This impact should not be taken lightly, especially given that two out of five adults who don’t smoke and half of all US children are exposed to secondhand smoke.

In assessing a patient’s risk for lung cancer, it is important to not only consider their own smoking habits but the habits of those around them including spouses, parents, children, etc. Unfortunately, more than 7,000 individuals who have never touched a cigarette die from lung cancer each year simply from secondhand smoke.

Radon exposure is another common yet relatively unknown contributor to lung cancer. Radon is a naturally occurring gas derived from rocks and dirt that can easily become trapped in buildings and homes. It is colorless, tasteless, and odorless, making its presence difficult to identify. The US Environmental Protection Agency (EPA) attributes radon exposure to approximately 20,000 lung cancer cases diagnosed each year, making it the second leading cause of lung cancer, following smoking. About 1 in every 15 US homes has high radon levels. As a preventative measure, the EPA recommends testing homes for radon and taking action if the levels exceed allowable limits.

Other environmental risk factors include workplace exposures that increase the risk of lung cancer, such as exposure to asbestos, arsenic, diesel exhaust, etc. A patient’s work environment is an important risk factor to assess for the development of lung cancer. In patients who smoke and are exposed to workplace environmental factors, the risk of developing lung cancer may be tremendously increased.

Additionally, an alarming risk factor is simply the air quality that we all share. Poor air quality due to air pollution has been attributed to the development of lung cancer.

“By delivering on the promise of a clean air generation we can reduce the number of lung cancers among those who have never smoked,” according to Dr. Cosford.

Cancer in non-smokers is epidemiologically different

In addition to highlighting the various underlying risk factors that may lead to the development of lung cancer in never-smokers, Dr. Cosford and coauthors suggested that there is a different mechanism by which non-smokers are afflicted with lung cancer. Specifically, lung cancer in non-smokers is almost exclusively non-small-cell lung cancer compared with the predominant small-cell lung cancer strongly associated with smokers. The authors also pointed out the disproportionate risk of non-smoker lung cancer in women vs men.

“Drawing attention to the contribution of underlying risk factors to lung cancer in never-smokers presents opportunities to reinforce efforts to tackle other major public health challenges,” said Dr. Peake. “For example, the impact of passive smoking and air pollution on lung cancers adds weight to the government's ambitions to improve air quality, and the public, clinicians, and policy makers must all be aware of this relationship.”

Overall, it is important to raise awareness of lung cancer in non-smokers to prompt earlier diagnosis, prevent delays in treatment, eliminate the stigma associated with lung cancer, and balance the research efforts that will ultimately help physicians improve their care.