Smoking and lung cancer

In the United States, approximately 85% of all lung cancers are in people who smoke or who
have smoked . Lung cancer is fatal for most patients. The estimated number of deaths of lung
cancer will exceed 1.3 million annually early in the third millennium . Lung cancer is the leading
cause of cancer-related deaths among Americans of both genders, with 174,470 estimated newly
diagnosed cases and 162,460 deaths . The number of deaths due to lung cancer exceeds the

annual number of deaths from breast, colon, and   prostate cancer combined . Recent advances in technology have enabled earlier diagnoses, and advances in surgery, radiation therapy, imaging, and chemotherapy have produced improved responses rates. However, despite these efforts, overall survival has not been appreciably affected in 30 years, and only 12–15% of patients with lung cancer are being cured with current treatment approaches . The prognosis of lung cancer depends largely on early detection and immediate, premetastasis stage treatment . Prevention of lung cancer is the most desirable and cost-efficient approach to eradicating this deadly condition. 

Numerous epidemiologic studies consistently define smoking as the major risk factor for lung cancer. The causal role of cigarette smoking in lung cancer mortality has been irrefutably established in longitudinal studies, one of which lasted as long as 50 years Tobacco smoke, which is inhaled either directly or as second-hand smoke, contains an estimated 4000 chemical compounds, including over 60 substances that are known to cause cancer . Tobacco irritants and carcinogens damage the cells in the lungs, and over time the damaged cells may become cancerous. Cigarette smokers have lower levels of lung function than nonsmokers , and quitting smoking greatly reduces cumulative risk for developing lung cancer .

 The association of smoking with the development of lung cancer is the most thoroughly documented causal relationship in biomedical history . The link was first observed in the early 1950s through the research of Sir Richard Doll, whose pioneering research has, perhaps more so than any other epidemiologist of his time, altered the landscape of disease prevention and consequently saved millions of lives worldwide. In two landmark US Surgeon Generals’ reports published within a 20-year interval (in 1964 and in 2004 )iterature syntheses further documented the strong link between smoking and cancer. Compared to never smokers, smokers have a 20-fold risk of developing lung cancer, and more than 87% of lung cancers are attributable to smoking . The risk for developing lung cancer increases with younger age at initiation of smoking, greater number of cigarettes smoked, and greater number of years smoked .Women smoking the same amount as men experience twice the risk of developing lung cancer