The majority of lung cancers (about 85 to 90 percent) are due to cigarette smoking. A number of diverse genetic abnormalities have been identified in lung cancer cells. Some of these genetic abnormalities may be causal (i.e., responsible for initiating the development of cancer), while others may instead indicate the progression of the cancer.
Not everyone who smokes will develop lung cancer. Studies have identified that normal genetic variations in the population, known as "polymorphisms," may make some individuals more likely to develop lung cancer if they smoke than other smokers (without the polymorphism).
Genetic polymorphisms may also be important for nonsmokers, some of whom are still exposed to tobacco smoke at work or in the home. Certain genetic polymorphisms have been found to be associated with a statistically greater risk of lung cancer development, even in a person who has never smoked. This may explain why relatives of persons with lung cancer, regardless of whether they smoke or not, have an increased chance of developing lung cancer. Additional studies are needed to better understand these gene-environment interactions.