What is lung cancer?

Lung cancer is a malignant tumor of the lungs and the most malignant tumor worldwide. In 2004, approximately 173,770 new cases of cancer of the lung and bronchus were estimated to occur. Lung cancer is the most frequent cause of cancer death and accounts for 14% of all cancer diagnoses and 28% of all cancer deaths. Death is usually due to metastatic spread, caused by our relative inability to diagnose the disease at its early, curative stages. The deaths attributed to lung cancer in 2004 were approximately 160,440, exceeding the combined total deaths of breast, prostate, and colorectal cancer patients. Lung cancer is the most common cause of cancer death in women and the second most common cause of cancer death in men.

Cigarette smoking is unequivocally the most important risk factor in the development of lung cancer. Other environmental factors that may predispose to lung cancer include industrial substances such as asbestos, arsenic, chromium or nickel; organic chemicals; radon or iatrogenic radiation exposure (as a result of treatment); air pollution; and other environmental (secondary) smoke in nonsmokers. These factors contribute to the development of lung cancer due to their association with a progressive set of genetic changes that transform a normal cell into a malignant cell.