The majority of lung cancer deaths (about 80%) 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 (for example, 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 — polymorphisms — in the population 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 greater risk of lung cancer development, even in a person who has never smoked. This may explain why relatives of people 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.