Date Published: 05/23/2010 [Source]
Cigarette smoking is the most important cause of lung cancer. Research as far back as the 1950s clearly established this relationship. Cigarette smoke contains more than 4,000 chemicals, many of which have been identified as causing cancer.
A person who smokes more than one pack of cigarettes per day has a risk of developing lung cancer 20-25 times greater than someone who has never smoked.
Once a person quits smoking, his or her risk for lung cancer gradually decreases. About 15 years after quitting, the risk for lung cancer decreases to the level of someone who never smoked. Cigar and pipe smoking increases the risk of lung cancer, but not as much as smoking cigarettes. Other causes of lung cancer include the following:
Passive smoking presents another risk for lung cancer. An estimated 3,000 lung cancer deaths occur each year in the U.S. that are attributable to passive smoking.
Air pollution from motor vehicles, factories, and other sources probably increase the risk for lung cancer, and many experts believe that prolonged exposure to polluted air is similar to prolonged exposure to passive smoking in terms of risk for developing lung cancer.
Radon exposure poses another risk. Radon is a by-product of naturally occurring radium, which is a product of uranium. Radon is present in indoor and outdoor air.
The risk for lung cancer increases with significant long-term exposure to radon, although no one knows the exact risk. An estimated 12% of lung cancer deaths are attributable to radon gas, or 15,000 to 22,000 lung cancer-related deaths annually in the U.S. Radon gas is the second leading cause of lung cancer in the U.S. As with asbestos exposure, smoking greatly increases the risk of lung cancer with radon exposure.
Lung Cancer Survival Rates
Several factors influence lung cancer survival rates. The type of cancer, the stage it is at when diagnosed, and the overall condition of the patient all play a role in determining survival. Cancer survival is usually expressed in terms of a five-year survival rate, which is the percentage of patients with cancer who survive at least five years after their cancer is diagnosed.
Studies have shown that five-year survival rates among non-small cell lung cancer patients vary by stage. Stage 0 patients have the best survival, of close to 50% at five years. Approximately one-quarter of stage II patients survive to five years, as compared to 8% of stage III patients and only 2% of stage IV patients. In general, small cell lung cancer tends to proceed more rapidly to terminal disease. Ten to fifteen percent of patients with limited-stage small cell lung cancer, and between one and two percent of those with extensive-stage cancer, survive to five years.
Estimates of cancer survival do not reflect current treatment advances that may lead to better chances of survival, because they are typically calculated for a five-year period that does not include the previous year. Further, each patient responds to treatment in a unique way; aggregate estimates do not account for individual factors that may improve or worsen the likelihood of survival.
The overall number of deaths in the United States from lung cancer rose throughout the 1980s, and began to drop for men in the 1990s. However, a similar decrease has not been observed among women. Over fifty thousand current and former smokers have been enrolled in the National Lung Screening Trial to find out if chest x-rays and CT scans taken before the onset of lung cancer symptoms may improve early diagnosis and therefore survival.