Lung Cancer in Non-Smokers

Differences in Lung Cancer Between Non-Smokers and Smokers

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Smoking is the greatest risk factor for developing lung cancer, but that doesn't mean non-smokers are completely protected from the disease. In fact, globally, about 25% of lung cancer patients have never smoked. In many ways, lung cancer in non-smokers is a different disease than lung cancer in smokers with causes, treatments, and survival rates differing significantly among those who have never smoked or smoked fewer than 100 cigarettes in their lifetime compared to current or former smokers.

Lung Cancer Non-Smokers
  • Among never-smokers, women are more likely than men to develop lung cancer.

  • Never-smokers with lung cancer live 56% longer than current smokers with the disease.

  • Adenocarcinoma is the most common diagnosis.

Lung Cancer Smokers
  • Among smokers, men are more likely than woman to develop lung cancer.

  • Risk of death for smokers with lung cancer is 29% to 39% higher than for never-smokers.

  • Squamous cell carcinoma is the most common diagnosis.

Source: Survival among never-smokers with lung cancer in the cancer care outcomes research and surveillance study.

In recent years, researchers have seen the proportion of never-smokers with non–small-cell lung cancer more than double (from 13% to 28%). Understanding what might put you at risk for lung cancer and how you can protect your health is essential for everyone.

Why Non-Smokers May Develop Lung Cancer

Without a doubt, cigarette smoking has the greatest influence on your chances of developing cancer. But there are other causes of the disease, which is why non-smokers can develop lung cancer as well.

Lung cancer tends to be diagnosed at a younger age in non-smokers compared to smokers. In these instances, the disease is usually traced to one of several factors.

Environmental Exposures

Exposure to various environmental substances can raise your risk of lung cancer.

These include:

  • Radon: Radon is a radioactive gas produced when uranium naturally breaks down in soil. It's possible for radon to be present in your home without you knowing it. Exposure to radon gas is the leading cause of lung cancer in non-smokers.
  • Secondhand smoke: Secondhand smoke includes smoke exhaled by a smoker and smoke emitted from the lit end of a cigarette, pipe, or cigar, or from tobacco burning in a hookah. This type of smoke is responsible for approximately 7,330 lung cancer deaths each year.
  • Asbestos: This naturally occurring silicate has been used in home insulation, auto manufacturing, shingles, ceiling tiles, flooring, and other everyday materials. If the long and thin, fibrous crystals that make up asbestos are released into the air and inhaled, they can cause serious lung damage, including mesothelioma, a cancer of the lung lining.
  • Air pollution: A study of 17 European countries found a direct correlation between air pollution and lung cancer; researchers estimated that air pollution was responsible for 15% of worldwide lung cancer deaths.

Occupational Exposure

Carcinogenic chemicals and substances are significant causes of lung cancer. Some jobs can increase your exposure to these cancer-causing agents such as arsenic, chromium compounds, nickel compounds, and polycyclic aromatic hydrocarbons (PAHs). High-risk occupations include:

  • Truck driving
  • Sandblasting
  • Metalworking
  • Printing
  • Ceramic making
  • Uranium mining
  • Glass manufacturing

It's estimated that in the United States, occupational exposures contribute to between 13% and 29% of lung cancers in men and roughly 5% in women.

Genetics

Although it's not often associated with lung cancer, the disease can run in families (similar to breast cancer). Having a genetic disposition requires close monitoring and testing. If you have a blood relative who was diagnosed with lung cancer, discuss it with your doctor.

Interestingly, researchers have also found that lung cancer in non-smokers may be characterized by certain types of genetic mutations not found in tumors of smokers who develop lung cancer. Because of this, targeted therapies aimed at these mutations (for example, drugs that work on EGFR mutations) may work better in never-smokers.

Gene testing (molecular profiling) can now be done to detect these molecular changes.

Human Papillomavirus (HPV)

The most common sexually transmitted infection, HPV affects 79 million Americans. Those infected with the disease may develop warts on or around the genitalia, but many have no symptoms at all.

Several studies since the 1980s have looked at whether HPV infection increases the risk for lung cancer, especially among non-smoking women. Reviews of these studies do not show a clear connection between the sexually transmitted infection and lung cancer, and some have found that there is no association at all. It may be an area, though, that researchers continue to investigate.

Most Common Types of Lung Cancer in Non-Smokers

Non-smokers are more likely to develop specific types of cancer. Because they have no history of tobacco use, the signs for these cancers are sometimes dismissed as other conditions.

Adenocarcinoma 

This is the most common type of cancer among non-smokers. Adenocarcinomas are tumors that usually grow in the outer regions of the lungs and can be present for a long time before symptoms occur.

In many instances, adenocarcinoma will have already started to spread to other regions of the body (such as bones) before a diagnosis is made.

Bronchoalveolar carcinoma (BAC) is a subcategory of lung adenocarcinoma. It's a form of lung cancer that's common in non-smokers, especially young, female never-smokers. For unknown reasons, the incidence of BAC appears to be increasing worldwide.

Surgery is the first course of treatment if adenocarcinoma is caught in the early stages. Chemotherapy may be used after surgery to eradicate any cancer cells that can't be detected but may still be in your system.

Squamous Cell Carcinomas

More than half of lung cancers in smokers are classified as squamous cell lung cancers (a type of non-small cell lung cancer). This type of cancer may affect non-smokers but is significantly less common than other types.

Squamous cell lung cancers are associated with tumors that grow in the center of the lungs, usually in the larger bronchi that join the trachea to the lungs.

Depending on the stage of squamous cell carcinoma of the lungs, treatment may include surgery, chemotherapy, radiation therapy, targeted therapy, immunotherapy, or a combination of these. 

Everyone who is diagnosed with non-small cell lung cancer—and especially non-smokers—should have genetic testing done on their tumors via a lung tissue biopsy or a liquid biopsy (a blood test).

Mesothelioma

Mesothelioma normally the result of asbestos exposure, gives rise to malignant tumors that begin in the membrane that lines and protects the lungs, heart, and abdominal cavity.

There are three main types of mesothelioma with pleural mesothelioma being the most common. Pleural mesothelioma causes tumors to grow in the lining of the lungs.

Surgery, chemotherapy, and radiation therapy may be considered to treat the cancer or to provide palliative care if it's clear that curing the disease is not possible.

Symptoms

Since the types of lung cancer and their causes are usually different in non-smokers versus smokers, it's common for symptoms of the disease to also be different.

With lung adenocarcinomas being the most common type of cancer among non-smokers, early symptoms of lung cancer are likely to be missed. These include:

  • Fatigue
  • Slight shortness of breath
  • Upper back or chest pain

As the disease progresses, the symptoms will be similar to the signs associated with all types of lung cancer:

In cases of mesothelioma, shortness of breath and chest pain might be accompanied by swelling of the face and arms, trouble swallowing (feeling like food gets stuck), an irregular heartbeat, and pain in the shoulder, chest, or lower back. Depending on the type of mesothelioma you have, blood clots may also develop in the advanced stages of the disease.

Prognosis

Lung cancer in non-smokers is often diagnosed at a late stage, being first attributed to a respiratory infection or even allergies.

Still, some (but not all) studies suggest that overall survival is better in non-smokers. This difference is most apparent for those who are diagnosed at an early stage of the disease.

Female non-smokers, in general, also have a better prognosis than male non-smokers with lung cancer.

Research Focus

Researchers continue to work to figure out ways to detect lung cancer in non-smokers at an earlier stage. In the future, doctors may be able to test for tumor markers, substances in the blood associated with cancer, to find these cancers in non-smokers at the earliest, most treatable stages.

Prevention

lung cancer prevention in non-smokers
Verywell / Luyi Wang

Checking your home for radon and avoiding secondhand smoke are the most important things you can do to lower your risk of lung cancer as a non-smoker.

Certain dietary practices, as well as moderate amounts of exercise, appear to lower risk as well.

For those who work in occupations that have a high cancer risk, it's essential that you discuss precautions with your employer. The use of personal protective equipment, especially respiratory protection, should be assured; air quality should be regularly assessed to ensure low levels of carcinogens; and regular medical examinations should be conducted.

A Word From Verywell

Non-smokers who develop lung cancer may feel misunderstood. Due to the stigma of lung cancer, some people may assume that those with the disease "brought it upon themselves by smoking."

Such insensitive comments can make anyone feel alienated, whether they are smokers or non-smokers. In fact, research notes that lung cancer patients frequently comment that they feel less supported than people with other forms of cancer.

Don't let this prevent you from sharing your struggles with others and seeking help when you need it. While such comments may be distressing to hear, know that, oftentimes, they come from a place of unawareness. Surround yourself with positive individuals who can provide you with the support you need.

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