Lung Cancer Prevention (PDQ®): Prevention - Health Professional Information [NCI] - Description of the Evidence
Factors associated with increased risk of lung cancer
The most important risk factor for lung cancer (and for many other cancers) is cigarette smoking.[11,12,13] Epidemiologic data have established that cigarette smoking is the predominant cause of lung cancer. This causative link has been widely recognized since the 1960s, when national reports in Great Britain and the United States brought the cancer risk of smoking prominently to the public's attention. The percentages of lung cancers estimated to be caused by tobacco smoking in males and females are 90% and 78%, respectively. The manufactured cigarette has changed over time, but there is no evidence to suggest that changes such as "low tar" or "low nicotine" cigarettes have resulted in reduced lung cancer risks. Cigarette smoking is the most important contributor to the lung cancer burden because of its high prevalence of use and because cigarette smokers tend to smoke frequently, but cigar and pipe smoking have also been associated independently in case-control and cohort studies with increased lung cancer risk.[14,15] The cigar risks are of particular concern because of the increased prevalence of cigar use in the United States.
The development of lung cancer is the culmination of multistep carcinogenesis. Genetic damage caused by chronic exposure to carcinogens, such as those in cigarette smoke, is the driving force behind the multistep process. Evidence of genetic damage is the association of cigarette smoking with the formation of the DNA adducts in human lung tissue. A strong link between tobacco smoke and lung carcinogenesis has been established by molecular data.[17,18]
Secondhand tobacco smoke
Secondhand tobacco smoke is also an established cause of lung cancer. Secondhand smoke has the same components as inhaled mainstream smoke, though in lower absolute concentrations, between 1% and 10% depending on the constituent. Elevated biomarkers of tobacco exposure, including urinary cotinine, urinary NNK metabolites, and carcinogen-protein adducts, are seen in those who are exposed to secondhand cigarette smoke.[20,21,22]
A positive family history of lung cancer is a risk factor for lung cancer. The results of a meta-analysis of epidemiologic studies indicated that those with a positive family history of lung cancer were at approximately twice the risk of lung cancer compared with those with no affected relatives.[23,24] Cigarette smoking behavior tends to run in families and family members are exposed to secondhand smoke, so the extent to which measured family history represents a genetic predisposition to lung cancer independent of the shared risk factor of cigarette smoking is uncertain.