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Non-Small-Cell Lung Cancer

What is non-small-cell lung cancer?

Cancers are diseases in which normal cells transform so that they grow and multiply without normal controls. In many types of cancer, this results in the growth of one or more large masses, or tumors, of these transformed cells. Such transformed cells are said to have become malignant and are then called cancer cells. This can happen in almost any part of the body. When cancer starts in the cells normally found in the lungs, the disease is called lung cancer.

Lung cancer is one of the most common types of cancer and is the leading cause of death from cancer in men and in women. This is because the lungs are exposed to the external environment more than most other organs are. In many cases, cancer-causing substances (carcinogens) in the air are inhaled and cause cell damage that later becomes cancer. The most common cause of lung cancer, by far, is smoking.

Two main types of lung cancer exist: small cell lung cancer and non-small-cell lung cancer. Non-small-cell lung cancer is a catchall term for all lung cancers that are not small-cell type. They are grouped together because the treatment is often the same for all non-small-cell types. Together, non-small-cell lung cancers, or NSCLCs, make up a majority of lung cancers. Each type is named for the types of cells that were transformed to become cancer. The following are the 3 most common types of NSCLC in the United States:

Like all cancers, lung cancer is most easily and successfully treated if it is caught early. An early-stage cancer is less likely to have grown to a large size or to have spread to other parts of the body (metastasized). Large or metastasized cancers are much more difficult to treat successfully.

Non Small Cell Lung Cancer Causes

Tobacco smoking

  • Tobacco smoking is the cause of lung cancer in as many as 90% of cases.
  • A person who smokes is 13.3 times as likely to develop lung cancer as is a person who has never smoked. The risk also varies with the number of cigarettes smoked per day; people who smoke more than 20 cigarettes per day have a much greater risk of developing lung cancer than do those who smoke fewer than 20 cigarettes per day.
  • Once a person quits smoking, the risk of lung cancer increases for the first 2 years and then gradually decreases, but the risk never returns to the same level as that of a person who has never smoked.
  • Not all people who smoke develop lung cancer, and not all people with lung cancer ever smoked. Clearly, other factors, including genetic predisposition, also play a role.

Passive smoking (secondhand smoke)

  • Some lung cancer cases involving nonsmokers may be caused by secondhand smoke.
  • The Environmental Protection Agency has recognized passive smoking as a potential cause of cancer.


  • Asbestos exposure has been linked to lung cancer and other lung diseases.
  • The silicate type of asbestos fiber is an important carcinogen.
  • Asbestos exposure increases the risk of lung cancer by as much as 5 times.
  • People who both smoke and have been exposed to asbestos are at an especially high risk of developing lung cancer.


  • Radon is a gas produced as a result of uranium decay. Radon exposure is a risk factor for lung cancer in uranium miners.
  • Radon exposure is believed to account for a small percentage of lung cancers each year.
  • Household exposure to radon has never been clearly shown to cause lung cancer.

Other environmental agents

Exposures to the following agents account, at least partly, for some cases of lung cancer:

  • Petroleum-based chemicals called aromatic polycyclic hydrocarbons
  • Beryllium
  • Nickel
  • Copper
  • Chromium
  • Cadmium
  • Diesel exhaust
Medically Reviewed by a Doctor on 8/15/2016
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