Lung cancer
There are currently about fifty million smokers in the U.S. and there are another fifty million ex-smokers. Cigarette smoking has been linked to several human malignancies. Some of these links like the relationship between smoking and lung cancer are well established. In some other cases the relationship between smoking and cancer is not very well established. However several studies have clearly shown the malignant potential of chemical substances in cigarette smoke. This article is an attempt to summarize some of the known links between cigarette smoking and caner.
Lung cancer has a strong association with smoking. On average, smokers increase their risk of lung cancer between 5 and 10-fold compared to never smokers. Even though lung cancer can occur in non-smokers, it should be appreciated that more than 90 percent of all lung cancer patients are current or past smokers. Some sub types of lung cancer like small cell lung cancer is more strongly associated with smoking than others. There is plenty of research evidence in the literature linking lung cancer to smoking. A recent study published in the British Journal Of Medicine (Ref: BMJ 1997) concluded that the accumulated evidence support the fact secondhand exposure to cigarette smoke could lead to lung cancer.
Cancers of the head and neck area
Researchers have long noted the link between smoking and increased risk of head and neck cancers (squamous cell cancers) including cancer of the oral cavity, pharynx and the larynx. Men who smoke have a 27-times higher rate of oral cancer than men who have never smoked. For cancer of the larynx the risk is increased 12 fold among smokers compared to those who have never smoked. Alcohol overuse has a very significant multiplying effect on the risk in those who are smokers (Ref: Cancer Epidemiology Biomarkers and Prevention, 1997).
Cancer of the urinary bladder and kidneys
In developed countries cigarette smoking is the single most important cause of bladder cancer, accounting for an estimated 40-70% of all cases. Smokers have 2 to 3 fold increased risk of developing bladder cancer and kidney cancer compared to those who have never smoked. A chemical that is present in cigarette smoke called, polyaromatic hydrocarbons are thought to be the culprit for increased risk of bladder cancer (Ref: Cancer Epidemiology, Biomarkers and Prevention 2006).
Cervical cancer
Cigarette smoking has been linked to development of cervical cancer. In a recently published study by the International Collaboration of Epidemiological Studies of Cervical Cancer analyzed data from 13,541 women with and 23,017 women without cervical carcinoma, from 23 epidemiological studies. The study found that current smokers had a 1.6 fold increased risk of developing squamous cell carcinoma of the cervix compared to never smokers. The risk increases with the number of cigarettes smoked per day and with younger age at starting smoking (Ref: International Journal of Cancer 2006).
Pancreatic cancer
Smoking is estimated to be responsible for 30% of pancreatic cancer. Similar to bladder cancer, carcinogens inhaled by the smoker are thought to enter the blood stream and reach the pancreas via the blood and also bile, secreted by the liver to aid digestion (Ref: IARC Monographs on the evaluation of carcinogenic risks to humans 2004).
Colon cancer
Smokers have an increased risk of developing colon cancer compared to never smokers. The increased risk of colon cancer is thought to be due to the transport of carcinogens to the colon from inhaled or swallowed tobacco smoke. Data supporting this association come from several longitudinal studies in which groups of people are followed over many years to record the occurrence of various illnesses. Smoking is thought to double the risk of developing colon cancer (Ref: IARC Monographs on the evaluation of carcinogenic risks to humans 2004).
Esophageal cancer
Smokers have a significantly higher risk of developing squamous cell cancer of the esophagus compared to never smokers. Like squamous cell cancer of the head and neck areas the risk is multiplied by over use of alcohol together with smoking (Ref: IARC Monographs on the evaluation of carcinogenic risks to humans 2004).
Breast Cancer
Data on links between breast cancer and smoking have been mixed, and this has led to conflicting health messages. Among Danish women interviewed at the time of mammography, smoking for more than 30 years was associated with a 60% higher risk of breast cancer and onset at an average of eight years earlier, when compared with nonsmokers.
Given that breast cancer incidence is soon to be eclipsed by lung cancer incidence among women, further data clarifying the role of smoking in causing breast cancer should be of value in strengthening efforts to inform and assist women to quit smoking (Ref: Int J Cancer 2002).
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