Unless otherwise indicated, information in this section is from Reference 3.
Tobacco smoke contains 43 known carcinogens,(1) including a number of known organ specific carcinogens, and compounds which assist with the formation of carcinogens within the body. Carcinogens and carcinogenic metabolites are carried through the body in the bloodstream, following absorption through the lungs. Smoking also affects metabolism and enzyme activity, which may affect carcinogenesis.
Cigarette smoking is a major cause of cancers of the oral cavity, oesophagus and larynx. Risk is raised with increased exposure to smoke, and diminishes with a decrease in tobacco consumption. The use of alcohol in combination with smoking acts synergistically to greatly increase the risks for these cancers.
Heavy smokers have a laryngeal cancer mortality risk 20 to 30 times greater than that of non-smokers. Smokers of low tar cigarettes have been shown to have a lower risk of developing cancer of the larynx, but still have a much higher risk than non-smokers.
Long term use of smokeless tobacco (chewing tobacco or snuff) is a factor in the development of cancers of the oral cavity, particularly cancers of the cheek and gum (see also Chapter 9).
In men, approximately 57% of cancers of the oral cavity and pharynx, 54% of cancers of the oesophagus and 73% of cancers of the larynx can be attributed to smoking. For women, the attributable fractions are 51% of cancers of the oral cavity and pharynx, 46% of cancers of the oesophagus and 66% of cancers of the larynx which can be attributed to smoking.
Smoking is a cause of bladder cancer.(2) Forty-three percent of male and 36% of female bladder cancers can be attributed to smoking.(4)
Cigarette smoking is at least a contributory factor and possibly a causal factor in development of cancers of the parenchyma and pelvis of the kidney. Smoking has been estimated to be a factor in 28% of cancers of the kidney parenchyma in males and 21% in females, and 55% of cancers of the kidney pelvis in males and 48% in females.(4)
Cigarette smoking is at least a contributory and may be a causal factor in the development of pancreatic cancer. It is estimated that 24% of pancreatic cancer in males and 19% in females is attributable to smoking.(4)
Epidemiological studies have shown an association between cigarette smoking and stomach cancer. It is estimated that 14% of stomach cancer in men and 11% in women can be attributed to smoking.(4)
Women who smoke cigarettes have a greater risk of developing cancers of the cervix and vulvar. For cervical cancer, the relationship appears to be dose-responsive, with one study finding an 80% increased risk of developing the cancer among heavy smokers.(40) It is estimated that 19% of all cases of cervical cancer and 40% of vulvar cancer are caused by smoking.(4)
Increased risk of penile cancer is associated with smoking. It is estimated that 30% of cancers of the penis are caused by cigarette smoking.(4)
Research indicates that there are increased risks associated with smoking and cancers of the anus.(41) Overall, 48% of anal cancer in males and 41% in females is caused by smoking.(4)
Since the mid 1980s, research has increasingly linked smoking with certain types of leukaemia.(42,43,44,45,46,47) A high strength of association in some studies has led to speculation that the relationship may be causal.(48,49) However, this has not been a consistent finding(50,51) and further research is required.
Liver cancer is relatively uncommon in developed countries, but a major cause of death in many developing countries.(52) Chronic infection with Hepatitis-B virus and exposure to food-borne carcinogens are considered high risk factors in these populations. In populations where exposures to these risk factors are low or negligible, research is increasingly suggesting that smoking may be an independent risk factor for liver cancer.(53) However, the lack of consistency among studies does not favour a causal interpretation.(4)
Bronchioloalveolar carcinoma is a particular type of cancer found in the alveolar space (the small air sacs within the lungs, where oxygen is transferred into the bloodstream). This cancer is clinically and pathologically different from other cell types of lung cancer, and until recently was thought to be unrelated to smoking, due to its comparatively high incidence among non-smokers.
Recent research now suggests that for a majority of cases, bronchioloalveolar carcinoma is related to smoking. However due to its level of incidence among non-smokers, tobacco use cannot be considered the only factor in disease causation.(54)
Although smoking has not been shown to be responsible for the development of prostate cancer, smokers may be at greater risk for more aggressive disease, or cancer that advances more rapidly.(54a) A recent study found higher death rates from prostate cancer in current cigarette smokers.(54b)