Lung Cancer: The Basics

What are the lungs?

The lungs are two spongy organs found in the chest. They are responsible for delivering oxygen to the bloodstream. When you take a breath in, air moves into the lungs causing them to expand. The air can then come very close to blood that is traveling in small vessels called capillaries. When you breathe out, you exhale substances that you don't need like carbon dioxide. The lungs are specially designed to place blood in close contact with as much air as possible, so their tissues are very delicate. The right lung has three sections called lobes. The left lung has only two lobes. Air comes in through your mouth and nose and then travels down a tube to the lungs called the trachea. The trachea divides into smaller branches called bronchi, and the bronchi keep dividing and dividing like branches on a tree. As the branches get smaller, they are called bronchioles. At the end of the branches, there are little sacs of air called alveoli. The air comes into contact with blood in the alveoli. The lungs are exposed to whatever you breathe in, so any toxic chemicals or pollutants in the air you breathe can get into your body through your lungs.

What is lung cancer?

Lung cancer happens when cells in the lung begin to grow out of control and can then invade nearby tissues or spread throughout the body. Large collections of cancer cells are called tumors. Cells in any of the tissues in the lung can develop cancer; but most commonly, lung cancer comes from the lining of the bronchi. Lung cancer is not really thought of as a single disease, but rather a collection of several diseases that are characterized by the cell type that makes them up, how they behave, and how they are treated. Lung cancer is divided into two main categories:

• Small cell lung cancer (SCLC) - the rarer of the two types (about 20% of all lung cancers), small cell lung cancer is more aggressive than non small cell lung cancer because is grows more quickly and is more likely to spread to other organs
• Non small cell lung cancer (NSCLC) - the more common of the two types (80% of all lung cancers), non small cell lung cancer is generally slower growing than small cell lung cancer and is divided into three different types based on how the cells look that make it up - adenocarcinoma, large cell carcinoma, and squamous cell carcinoma

Am I at risk for lung cancer?

Lung cancer is the most common cause of cancer death in the world for both men and women. In the United States alone, it is estimated that 163,510 people will die from lung cancer in 2005. In comparison, 127,500 people are expected to die from colon, breast and prostate cancer combined in 2005 (the 2nd, 3rd, and 4th most common cancers in the U.S.). In the U.S., there has been a striking increase in the number of women getting lung cancer; in the 1990s, lung cancer overtook breast cancer as the most common cause of cancer death amongst women. This probably reflects increase incidence of smoking among women.

Every smoker is at risk for lung cancer. It is estimated that 87% of all cases of lung cancer are caused by cigarette smoking. The major risk factor for lung cancer is cigarette smoking. Your risk of getting lung cancer from cigarette smoking increases the longer you smoke, the more you smoke, and the deeper you inhale. Smoking low tar cigarettes does not prevent you from getting lung cancer. Importantly, if you quit smoking, your risk of getting lung cancer declines. The longer you go without smoking, the greater your risk declines. It is never too late to quit because your risk declines somewhat no matter how long you have been smoking. Even patients who have been diagnosed with lung cancer have been demonstrated to respond to treatment better and live longer if they quit smoking at the time of their diagnosis.

Smoking also has an affect on people around you. Second-hand smoke, or smoke inhaled when you are near someone smoking, is another risk factor for lung cancer. It is estimated that 17% of cases of lung cancer in non-smokers are caused by second-hand smoke exposure in childhood and adolescence. Non-smoking spouses of smokers are 30% more likely than spouses of non-smokers to get lung cancer. Even though many people don't inhale them, smoking pipes and cigars is a risk factor for lung cancer as well. The more pipes or cigars you smoke, the more likely you are to get lung cancer. Although it is not as well established as cigarette smoking, smoking marijuana is also a risk factor for getting lung cancer. Both the magnitude and duration of marijuana use seems to be related to your overall risk.

Although smoking cigarettes is by far the most common and important risk factor for getting lung cancer, there are some environmental exposures that increase your risk for lung cancer as well. People who work with asbestos are more likely to get lung cancer; and if they smoke cigarettes too, their risk rises even higher. Asbestos is found in industries like shipbuilding, brake manufacture, insulation/fireproofing, and asbestos mining and production. Other workers who may have a higher risk of lung cancer are those exposed to arsenic, chromium, nickel, vinyl chloride, hard metal dusts, talc, uranium, and gasoline and diesel exhaust fumes.

Radon is an invisible, odorless gas that exists naturally in areas where there is a lot of uranium in the ground. Radon can collect in both uranium mines and peoples' houses. Exposure to radon has been associated with a slightly increased risk of lung cancer. You can check for radon with detectors available at a hardware store, and getting rid of it is usually as easy as opening a basement window.

People who have already had lung cancer are at risk for getting it again. A history of interstitial lung disease or tuberculosis (TB) also increases your risk of getting lung cancer. However, it should be stressed that cigarette smoking is far and away the most important and dangerous risk factor for developing lung cancer.