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Early Lung Cancer Detection
Tuesday, April 24, 2007
Lung cancer is the most common type of cancer. It is also responsible for the most cancer deaths in both men and women in the United States. It is estimated that over 213,000 new cases of lung cancer will be diagnosed in the U.S. in 2007 and that lung cancer will be responsible for over 160,000 deaths this year. Although the rate of lung cancer cases appears to be dropping among Caucasians and African-American men in the United States, it continues to rise among Caucasian women and African-American women. There are two major types of lung cancer: small cell and non-small cell lung cancer. Small cell lung cancer is responsible for 20% of lung cancer, and non-small cell lung cancer is responsible for 80% of cases. Non-small cell lung cancer includes squamous cell carcinoma, adenocarcinoma, and large cell carcinoma.
Smoking is the #1 cause of lung cancer. It is estimated that 87% of lung cancer cases are attributable to smoking. This is approximately 7 out of every 8 cases of lung cancer. Cigarette smoke has been shown to contain over 4000 different chemicals, and many of these are cancer-causing substances (carcinogens). The good news is that if you quit smoking, you reduce your risk of lung cancer. After 10 years of abstaining from smoking, lung cancer risk drops from one-third to one-half compared to those who continue to smoke.
Radon is thought to be the second leading cause of lung cancer in the U.S. Radon gas can be emitted from the soil, and it may enter homes through gaps and cracks in the foundation or insulation. It is estimated that radon is responsible for 14,000 to 22,000 lung cancer deaths each year in the U.S. and that 12% of all lung cancer deaths are linked to radon exposure. The Environmental Protection Agency (EPA) estimates that nearly one out of every 15 homes in the U.S. has indoor radon levels at or above the level which homeowners should take action (i.e., 4 picocuries per liter of air on a yearly average). You cannot see or smell radon gas, but you can have the radon level in your home tested.
Another factor that can increase the risk of lung cancer is exposure to asbestos. Asbestos has been used in insulation and brake linings; certain occupations can lead to a greater exposure to asbestos fibers, including jobs that involve working with insulation, brake linings, and coke ovens. The elevated risk of lung cancer for those who smoke and are exposed to asbestos is multiplicative rather than additive; i.e., there is a much higher risk of lung cancer from the combination of these two risk factors than that obtained by adding the risks of smoking and asbestos inhalation.
Other carcinogenic compounds include uranium, arsenic and certain petroleum products. There is also evidence that particulate matter pollution can cause lung cancer.
Lung cancer takes years to develop. In its early stages, it is asymptomatic. As the tumor enlarges, it may produce very nonspecific symptoms, including chronic cough, hoarseness, wheezing, and coughing of blood. With more advanced disease, there may be weight loss. A lung tumor may be responsible for repeated bouts of pneumonia.
Chest radiographs or "chest x-rays" can readily detect larger tumors in the lungs, but smaller masses, especially those less than a centimeter in size, can be difficult to see with standard chest radiographs. Computed tomography (CT) offers a more sensitive means for discovering tumors at an early stage. Computed tomography, also called CT scanning or CAT scanning, is a sophisticated form of x-ray examination. It involves passing an x-ray beam through multiple angles. This allows for the ability to reconstruct slices of the lungs in two dimensions. It can also permit three-dimensional renditions of lung tissue. CT images allow physicians to see the internal architecture of the lungs, in a way not possible with standard chest radiographs. There is a much greater sensitivity of computed tomography for small lung tumors than is achievable with standard chest radiographs. The trade-off is that there is a greater radiation exposure. Large-scale research studies evaluating the role of CT for early cancer detection are underway. CT appears to detect tumors at an earlier stage, but more research is needed before it is concluded that survival is prolonged and that CT can be advocated as a screening tool.Learn more about CAT scans: