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 contracting 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 never-smokers

  • Squamous cell carcinoma is the most common diagnosis

In recent years, researchers have seen the proportion of never-smokers with non–small-cell lung cancer more than doubled 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.

lung cancer prevention in non-smokers
Verywell / Luyi Wang

Causes

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 that can put you at risk for the disease.

Environmental Exposures

While cigarette smoking has the greatest influence on your chances of developing cancer, exposure to various environmental substances can also raise the risk. These include:

  • Radon: Radon is a radioactive gas produced when uranium naturally breaks down in the 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.

Genetic Predisposition

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.

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. However, 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.

Types

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. Being aware of how lung cancer manifests in never-smokers can help you be on the alert.

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 couldn't be seen but may 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 it is significantly less common.

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 lung.

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

Mesothelioma

This type of cancer, normally the result of asbestos exposure, gives rise to malignant tumors that begin in the membrane that lines and protect 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 no cure is possible.

Genetic Mutations

Researchers have 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.

Since some genetic mutations in cancer cells are more common in those who have never smoked, targeted therapies aimed at these mutations may work better in never-smokers.

Gene testing (molecular profiling) can now be done to detect these molecular changes. Targeted therapy to treat these mutations involve drugs that work on specific mutations such as the EGFR mutations.

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

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

Prevention

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.

Future Directions in Research

Research is currently in progress 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.

Support

Due to the stigma of lung cancer, non-smokers with lung cancer frequently comment that they feel less support than people with other forms of cancer. Insensitive comments, especially those that accuse a person of smoking, can be hurtful at best and harmful at worst. It can make individuals feel ashamed to share their struggles with others due to the stigma. Both smokers and non-smokers with lung cancer need our unconditional caring and support.

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