Lung cancer is the most common cause of cancer death not only in the United States, but also in the world. It accounts for more life lost than breast, prostate, colon, and rectal cancer combined. It is estimated that more than 172,000 cases of lung cancer were diagnosed in the United States in 2005, and over 160,000 patients succumbed to the disease. The majority of these cancers (approximately 85-90 percent) are directly linked to cigarette smoking.
Non-small cell lung cancer is the most common type of lung cancer, accounting for 75 percent of cases. Non-small cell lung cancer includes squamous cell carcinoma, adenocarcinoma, large cell carcinoma, and undifferentiated carcinoma.Small cell lung cancers grow more rapidly and tend to spread more quickly to other organs. They account for about 20 percent of lung cancers. Mesothelioma is a rare tumor of the lining of the lungs, often attributed to asbestos exposure, and represents 5 percent of lung cancer cases.
Great strides have been made in finding cures and new treatment options for this disease. New anticancer drugs, better staging and imaging techniques, and new surgical procedures have shown promise in the treatment of lung cancer.
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Like other cancers, lung cancer begins when the set of genetic instructions (the DNA) in certain cells becomes altered, or mutated, and the cells start growing out of control. Over the course of many years, one of these clusters of cells can become a tumor, and bits of the tumor may break off and travel throughout the body, producing new areas of cancer (metastasis).
Many different factors produce these initial genetic changes. Tobacco smoke, for instance, contains a host of cancer-causing chemicals that can alter the DNA. Still, some people who are thought not to have had significant exposure to these chemicals also develop lung cancer.
There are several known risk factors for lung cancer:
Cigarette smoking: Cigarette smoking is the most important risk factor in the development of lung cancer. It is estimated that as many as 90 percent of lung cancer diagnoses could be prevented if cigarette smoking were eliminated, some of them in nonsmokers who are exposed to secondhand smoke. Smoking cigars and pipes also causes cancer.
Increasing age: Lung cancer is more common in people who are over the age of 60.
Personal and family history of lung cancer: Having had a case of lung cancer in the past raises the odds that you will develop another. Also, if a close relative--a sibling or parent--has lung cancer, your odds of getting the disease are slightly higher.
Radon exposure: This odorless gas is formed when naturally occurring radium in soil and rocks decays. Radon gas can slip through cracks and other openings in the basement or ground floor of your house and build up, polluting the air. Long-term exposure to this gas puts you at higher risk of developing lung cancer.
Asbestos exposure: Asbestos is a tiny fiber formerly used in the construction industry. When inhaled, it can cause cancer. It is still present in many buildings but does not pose a danger to your health unless it is exposed. Asbestos also can cause the most rare form of lung cancer, mesothelioma, which begins in the lining of the lungs. Asbestos exposure coupled with smoking is particularly dangerous.
Other substances: Your risk of developing lung cancer is increased if you've been exposed to radiation, especially as a child, or certain chemicals, such as arsenic, in some smokestack emissions. Heavy exposure to traffic fumes also may put you at higher risk.
Personal history of tuberculosis and pneumonia: Having had these and other lung diseases raises the chances that you'll develop lung cancer because of the scars they may leave.
The lungs, two spongy organs located in the chest cavity (also called the pleural cavity), are where the body absorbs the oxygen gas needed to help fuel the body and gets rid of waste carbon dioxide gas. The lungs are not symmetrical; the right lung has three lobes, while the left has two (the heart takes up room on the left side).
The trachea, commonly called the windpipe, channels air into the lungs. The trachea diverges into tubes called bronchi (where many lung cancers start), and, like branches on a tree, those in turn split into smaller tubes known as bronchioles. The alveoli are the air sacs that sit on the end of the bronchioles, and it's there that the actual exchange of gases takes place. The lining of the lungs is called the pleura.
Last reviewed on 7/28/09
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