Awareness: November is Lung Cancer Awareness Month
What is Lung Cancer?
More people in the United States die from lung cancer than any other type of cancer. This is true for both men and women.
There are 2 major types of lung cancer:
Small cell lung cancer (SCLC)
About 10% to 15% of all lung cancers are small cell lung cancer (SCLC), named for the size of the cancer cells when seen under a microscope. Other names for SCLC are oat cell cancer, oat cell carcinoma, and small cell undifferentiated carcinoma. It is very rare for someone who has never smoked to have small cell lung cancer.
SCLC often starts in the bronchi near the center of the chest, and it tends to spread widely through the body fairly early in the course of the disease.
Non-small cell lung cancer (NSCLC)
About 85% to 90% of lung cancers are non-small cell lung cancer (NSCLC). There are 3 main subtypes of NSCLC. The cells in these subtypes differ in size, shape, and chemical make-up when looked at under a microscope. But they are grouped together because the approach to treatment and prognosis (outlook) are very similar.
Non-small cell lung cancer includes: squamous cell carcinoma, adenocarcinoma, large cell carcinoma, and other subtypes.
Other types of lung cancer
Carcinoid tumors of the lung account for fewer than 5% of lung tumors. Most are slow-growing tumors that are called typical carcinoid tumors. They are generally cured by surgery. Some typical carcinoid tumors can spread, but they usually have a better prognosis than small cell or non-small cell lung cancer. Less common are atypical carcinoid tumors. The outlook for these tumors is somewhere in between typical carcinoids and small cell lung cancer.
What are the risk factors for lung cancer?
Tobacco smoke - About 87% of lung cancer deaths are thought to result from smoking. The risk for lung cancer among smokers is many times higher than among non-smokers. The longer you smoke and the more packs a day you smoke, the greater your risk.
Radon - Radon is a naturally occurring radioactive gas that results from the breakdown of uranium in soil and rocks. It cannot be seen, tasted, or smelled. According to the US Environmental Protection Agency (EPA), radon is the second leading cause of lung cancer, and is the leading cause among non-smokers.
Asbestos - Workplace exposure to asbestos fibers is an important risk factor for lung cancer. Studies have found that people who work with asbestos (in some mines, mills, textile plants, places where insulation is used, shipyards, etc.) are several times more likely to die of lung cancer. In workers exposed to asbestos who also smoke, the lung cancer risk is much greater than even adding the risks from these exposures separately. It's not clear to what extent low-level or short-term exposure to asbestos might raise lung cancer risk. Both smokers and non-smokers exposed to asbestos also have a greater risk of developing mesothelioma, a type of cancer that starts in the pleura (the lining surrounding the lungs).
Radiation therapy to the lungs - People who have had radiation therapy to the chest for other cancers are at higher risk for lung cancer, particularly if they smoke. Typical patients are those treated for Hodgkin disease or women who get radiation after a mastectomy for breast cancer. Women who receive radiation therapy to the breast after a lumpectomy do not appear to have a higher than expected risk of lung cancer.
Arsenic - High levels of arsenic in drinking water may increase the risk of lung cancer. This is even more pronounced in smokers.
Family history - If you have had lung cancer, you have a higher risk of developing another lung cancer. Brothers, sisters, and children of those who have had lung cancer may have a slightly higher risk of lung cancer themselves, especially if the relative was diagnosed at a younger age. It is not clear how much of this risk might be due to genetics and how much might be from shared household exposures (such as tobacco smoke or radon). Researchers have found that genetics does seem to play a role in some families with a strong history of lung cancer.
Certain dietary supplements - Studies looking at the possible role of antioxidant supplements in reducing lung cancer risk have not been promising so far. In fact, 2 large studies found that smokers who took beta carotene supplements actually had an increased risk of lung cancer. The results of these studies suggest that smokers should avoid taking beta carotene supplements.
Air pollution - In cities, air pollution (especially from heavily trafficked roads) appears to raise the risk of lung cancer slightly. This risk is far less than the risk caused by smoking, but some researchers estimate that worldwide about 5% of all deaths from lung cancer may be due to outdoor air pollution.
How is lung cancer diagnosed?
Until recently, no lung cancer screening test had been shown to lower the risk of dying from this disease. Earlier studies of 2 possible screening tests, chest x-ray and sputum cytology, did find that these tests detected lung cancers at an early stage, but this did not improve a person's chance for a cure. For this reason, major medical organizations have not recommended routine screening with these tests for the general public or even for people at increased risk, such as smokers.
A newer type of CT scan, known as low-dose spiral CT (or helical CT) has shown some promise in detecting early lung cancers in heavy smokers and former smokers. Spiral CT provides more detailed pictures than a chest x-ray and is better at finding small abnormalities in the lungs. However, at this time, no major professional organizations, including the American Cancer Society, recommend routine lung cancer screening, either for all people or for those at increased risk.
The United States Preventive Services Task Force (USPSTF), a group of experts gathered together by the US government, has concluded that there's not enough evidence at this time to recommend for or against lung cancer screening in people without symptoms.
The American College of Chest Physicians (ACCP) does not recommend routine lung cancer screening at this time, advising that "individuals undergo screening only when it is administered as a component of a well-designed clinical trial.
The bottom line is -- people who are current smokers should realize that the best way to avoid dying from lung cancer is to stop smoking.
For more information on the diagnosis and treatment of lung cancer, please visit the American Cancer Society web page: www.cancer.org.
What we're doing at the Purdue University Center for Cancer Research: