Cancers caused by smoking cigarettes
This factsheet reviews the risks of developing various types of cancer from smoking or other tobacco use. Smoking is the biggest risk factor for and largest single cause of cancer and approximately one third of all cancer deaths are attributable to smoking. Globally, one in five cancer deaths are caused by tobacco.
In October 2009, scientists from 10 countries met at the International Agency for Research on Cancer (IARC) to reassess the carcinogenicity of several compounds, including tobacco. The review, published by The Lancet Oncology, concludes that there is sufficient evidence to confirm that smoking is a cause of 15 types of cancer: namely: cancer of the bladder, bone marrow (myeloid leukaemia, cervix, colorectum (large bowel), kidney, larynx (voice box), liver, lung, mouth (including lip and tongue), nose, oesophagus (gullet), ovaries, pancreas, pharynx (throat) and stomach. The
report also states that there is some evidence to suggest that smoking is a cause of breast cancer.
Lung cancer has been the most common form of cancer in the world for a number of decades, accounting for 1.61 million new cases and 1.38 million deaths every year.
Lung cancer is the cancer most commonly associated with smoking: around 85-90% of all lung cancers are caused by smoking, or as a result of exposure to second-hand smoke. Because of its poor prognosis, lung cancer is still the most common cause of cancer death. Fewer than ten percent of people with lung cancer will survive five years beyond diagnosis.
One in two persistent smokers will die of a smoking-related illness: of these, nearly one in four will die of lung cancer. Current smokers are fifteen times more likely to die from lung cancer than life-long non-smokers. Smokers who start when they are young are at an increased risk of developing lung cancer. Results of a study of ex-smokers with lung cancer found that those who started smoking before age 15 had twice as many cell mutations as those who started after age 20.
Cancers of the mouth and throat
Cigarette, pipe and cigar smoking are all major risk factors for cancers associated with the larynx, oral cavity and oesophagus. The risk for these cancers increases with the number of cigarettes smoked15 and those who smoke pipes or cigars experience a risk similar to that of cigarette smokers. It has been estimated that smoking is a cause of 85% of deaths from oral cancer (cancers of the lip, tongue, mouth and throat) amongst men in industrialised countries.
Heavy smokers have laryngeal cancer mortality risks 20 to 30 times greater than non-smokers. People who combined alcohol and tobacco use have a much higher risk of oral and pharyngeal (throat) cancers than those using tobacco or alcohol individually.
Smokeless tobacco, including chewing tobacco and snuff, has been associated with oral cancer for many decades. While the risk is considered small in comparison to smoking, a risk exists nevertheless. A US study comparing mortality rates among former smokers who switched to smokeless tobacco with those who stopped using tobacco altogether found that risks of dying from major tobacco-related diseases were higher among former cigarette smokers who switched to oral tobacco after they stopped smoking than among those who stopped using tobacco entirely.
Tobacco smoking is the principal preventable risk factor for bladder cancer in both men and women. The European Network of Cancer Registries states that bladder cancer is the 7th most common form of cancer amongst men and 14th amongst women and cites cigarette smoking as the principle risk factor. According to Cancer Research UK, the risk of developing bladder cancer is six times higher in current smokers than in people who have never smoked. As with lung cancer, the risk is associated with both the dose and duration of smoking, while cessation of smoking reduces the risk, returning to that of a non-smoker after 15 years.28
Most older studies found no association between smoking and breast cancer, but new evidence suggests that there is a link between nicotine and breast cancer. Researchers found that nicotine enhances the growth of breast cancer cells which means that smoking could be causally related to breast carcinogenesis and also that nicotine could directly contribute to the molecular mechanism of carcinogenesis. Other studies suggest that the increase in breast cancer risk mostly affects pre-menopausal women.
Colorectal/Colon cancer (large bowel)
The recent IARC update (2010) concludes that smoking is a cause of colon cancer. These findings are echoed by the World Health Organization and the Journal of the National Cancer Institute. There is some disagreement about the degree of risk and further research is needed to clarify the relative risk of smoking and colon cancer.
Kidney cancer accounts for just under 3% of all cancers in men and just under 2% in women living in the UK. Although comparatively rare, kidney cancer has consistently been found to be more common in smokers than in non-smokers and there is sufficient evidence to show that smoking is a risk factor for the two principal types of kidney cancer.
According to Cancer Research UK, smokers are twice as likely to develop kidney cancer than non-smokers. There is a dose-response relationship with an increase in the numbers of smoked per day. Risk appears to drop after smoking cessation. Approximately 24% of kidney cancer cases in men and 9% in women can be attributed to smoking.
Smoking has been found to be a cause of myeloid leukaemia but not lymphoid leukaemia in adults. There is some evidence to suggest that parental smoking can increase the risk of Acute Lymphoblastic Leukaemia (ALL) in children. A possible reason for this is the presence of benzene in the smoke.
Large case-control studies have demonstrated an association between smoking and risk of liver cancer. In many studies, the risk increases with duration of smoking or number of smoked daily. Confounding from alcohol can be ruled out in the best case-control studies by means of careful adjustment for drinking habits, as association with smoking has also been demonstrated among non-drinkers.
People who have a Hepatitis B or C infection have a higher risk of liver cancer if they smoke. Some studies have estimated this risk to be one hundred times higher compared to non-smokers who are not infected with the virus.
Researchers investigating the relationship between liver cancer and cigar smoking reported a seven-fold increase in risk. A separate study found a three-fold increase in risk for current cigar or pipe smokers.
Smoking has been found to increase the risk of cancer of the nose and sinuses, particularly for squamous-cell carcinoma. Cancer Research UK notes that even though nasal cancer is rare, smoking significantly increases the risk of developing the disease.
Oesophageal cancer (gullet)
Tobacco smoking is a cause of cancer of the oesophagus (gullet). Tobacco and alcohol, acting independently and together, are the main risk factors for squamous cell carcinoma of the oesophagus in Western countries. The risk increases with duration of smoking and also remains legated many years after smoking cessation.
Ovarian cancer is the fifth most common cancer in women in the UK and the most common gynaecological cancer. It has recently been included in the IARC list of cancers caused by smoking.
Smoking doubles a woman’s risk of a particular sub-type of the disease: mucinous ovarian cancer. Stopping smoking returns the risk to that of non-smokers in the long term.
Cancer of the pancreas is a rapidly fatal disease with a five-year survival rate of only 4%. The disease is caused by damage (mutations) to the DNA, with smoking a significant risk.