Primary lung cancer is a very serious respiratory disorder that begins in the airways and air sacs of the lungs.

What is going on in the body?

Cancer of the lung can begin in the lining of the trachea, the smaller airways, and the tiny air sacs. There are different types of lung cancer. Non-small cell lung cancer, or NSCLC, accounts for 70% to 80% of lung cancers. Small cell lung cancer or oat cell carcinoma, or SCLC, accounts for 25% of lung cancers. Both types can be fatal. They invade surrounding tissue and can spread to other parts of the body through the lymph nodes and bloodstream.

Lung cancer is the most common and most deadly cancer in the US. Roughly 160,000 deaths occur each year. Men and woman are equally affected. Most types of lung cancer are aggressive, spreading early in their course. Lung cancer can cause life threatening complications in the chest and spread to distant sites throughout the body causing death in this way. A person also may have symptoms which are reactions to tumors or a substance they make, called a paraneoplastic syndrome.

What are the causes and risks of the disease?

Inhaling tobacco smoke probably causes at least 90% of all lung cancer. Smokers have more than 30 times the risk of nonsmokers. A person's risk for lung cancer depends on how many packs of cigarettes he or she smokes each day and for how many years. People who quit smoking remain at risk, sometimes for decades. People exposed to radiation, radon, asbestos, and probably heavy metal are also at risk.

Lung cancer occurs if the cells lining the airways of the lungs are constantly exposed and stimulated by cancer-causing substances over several decades. This changes the genetic DNA, makeup of cells and results in the uncontrollable growth of abnormal cells.

It is very rare for a person who has not been exposed to cigarette smoke or radiation to develop small cell lung cancer. It occurs most often in middle aged and elderly people who have been exposed to cancer-causing poisons for several decades.