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Effects of Cigarette Smoking and Cancer Rates
Smoking is injurious to health and causes numerous deaths every year. In the United States along lung cancer mortality rates have been estimated to be around 100 men per 100000 aged between 50 and 54 (.Numerous research articles, funded studies and an extensive body of epidemiological data links cigarette smoking to a wide variety of cancers. Long time smokers have been found to suffer from cancers of the lung, head and neck, urinary tract, pancreas and the bladder. Other studies on smoking related cancers have also found that smoking can lead to an increased rate of leukemia and myeloma (Carbone, 1992). For long smoking has been associated with increased rates of lung cancer. However, recent studies have shown that smoking also causes increased rates of other cancers as well. In this paper, cancers linked to smoking will be investigated. It is hypothesized that there exists a popular and common misconception that smokers are at the risk of suffering mainly from lung cancer when they are at the risk of developing other forms of cancer too. The following four literature reviews attempt to demonstrate and support the hypothesis. the following papers contain studies about smoking related colorectal cancer, bladder cancer and cancers in the urethra, pelvis and upper digestive tract. Although the incidence of lung cancer is the highest among smokers, the possibility of other smoking induced cancer cannot be underestimated.
In a study by Liang, Cheng and Giovanucci (2002), it was found that there was a consistent association between smoking and colorectal cancer. Colorectal cancer in the cancer of the colon or the rectum. Their study was a synthesis of all the available data on smoking and colorectal cancer and was done by a comprehensive meta-analysis of all the studies that had been conducted so far. 36 previously existing studies were taken for their meta analysis and the results indicated that there was not only a persistent risk of colorectal cancer for smokers but that the incidence and the mortality rates for former smoker and current smokers differed. The study found that both current and past smokers had an increased risk of colorectal cancer incidence and mortality. The risk of mortality was higher in the case of current smokers as compared to the high rates of incidence found in former smokers. Continued smoking was found to increase the mortality rates as smoking is shown to increase tumor growth by suppressing cell-mediated immunity. Active smokers were also found to resist preventive and curative measures. There were however limitations to this study. Since this was a meta analysis of the other previous studies on smoking and colorectal cancer, the researchers were unable to get hold of primary data. Other significant studies on the same topic also had to be excluded because the time period of the studieswere too short. Studies on smoking and increased rates of cancer are also controversial because the cancer takes decades to form and spread and the studies are conducted only for a few years. Sustained decade old studies in this topic are few. Initial results were controversial because there was no evidence found between smoking and rectal cancers. This was due to the limited amount of time period of the study. Further studies have proved a link. However there needs to be more sustained studies on this topic to increase awareness about the link between smoking and colorectal cancer.
In a pooled study of cigarette smoking and pancreatic cancer (Lynch et al, 2009) it was found that smoking established a high risk factor for pancreatic cancer. However there was a limited number of studies when it came to examining the association of the intensity of smoking, the duration, dose and pancreatic cancer. The study consisted of an analysis of the pooled data from the international Pancreatic Cancer Cohort Consortium nested case-control study (1,481 cases, 1,539 controls). Using unconditional logistic regression, the odds ratios and confidence intervals were calculated. A comparative study between people who never smoked and active smokers revealed that active smokers had a significantly elevated risk of pancreatic cancer. The intensity of the risk increased with the more number of cigarettes smoked over a period of many years. But in the case of smokers who had quit for over 15 years, the risk of getting pancreatic cancer was similar to that of people who had never smoked in their lives. This finding suggested that quitting smoking reduces the risk of pancreatic cancer and that smoking only has a late-stage effect on pancreatic carcinogenesis. More studies of this nature should be conducted as they are direct studies and the results are more or less accurate. it also proves to show that quitting smoking does indeed reduce the risk of cancer and that it is not a mere misconception among people.
Smoking is also a leading cause of bladder cancer among men. A study on Cigarette smoking and bladder cancer, a pooled analysis of 11 case control studies (2000) proved that the primary risk for bladder cancer was cigarette smoking. The results of this study was enabled by pooling data of 11 case control studies which accurately measured the relationship between smoking and bladder cancer in men. Based on the information culled from 2600 men with cancer and 5524 controls together with duration of smoking, number of cigarettes a day and the period since quitting, it was found that active smoking and increased smoking directly leads to an increased rate in bladder cancer. A decrease in the number of cigarettes and smoking duration led to the decrease in the rate of bladder cancer. However quitting for many years did not lead to a state where the risk of bladder cancer was negligent like people who had never smoked. This is an important study as it was found that the estimates of the risk associated with smoking and bladder cancer was found to be higher than that of the previous studies conducted on this topic.
Oral cancer is caused not only by chewing tobacco, betel leaves, STD’s and alcohol consumption but also due to cigarette smoking. A study conducted on Taiwanese men ( Ko, 1995) found that all these factors were responsible for the increased rates of oral cancer among them. This paired hospital controlled study conducted on 104 male and 3 female patients with 194 male and 6 female controls found that the instances of oral cancer increased with smoking. Also smoking combined with alcohol intake and betel chewing was the worst cause of oral cancer among these patients. Tobacco and Tobacco smoke are carcinogens and target organs that includes the oral cavity, pharynx, larynx and the oesophagi. Although this study the combines effects of betel chewing , alcohol intake and tobacco on the increased risk of oral cancer, it also talks about the risks of oral cancer associated with tobacco use alone.
These studies indicate that cigarette smoking is the leading cause for other types of cancers such as pancreatic cancer, oral cancer, bladder cancer and colorectal cancer. They also indicate that the risks of cancer falls as the smoking behavior is reduced. While in some cancers quitting smoking did not lead to any change in the risks or rates of cancer, quitting played an important role in some. Smoking not only causes lung cancer (although incidences of lung cancer is high among smokers) but also other types of cancers. More research and studies should be focused on the association of smoking and these cancers so people could be better informed and the smoking rate could be brought down. There needs to be more studies on the impact of smoking on women as well as what specific cancers they are susceptible to in case of increased smoking.
References
Carbone, David. (1992). Smoking and Cancer. The American Journal of Medicine, 93(1), 513-517.
The detailed data files of the WHO Mortality Database. Geneva: World Health Organization. (2012). Retrieved from : http://www.who.int/whosis/mort/download/en/index.html.
Liang, S. Peter., Chen, Ting-ye., Giovannucci, Edward. (2008). Cigarette smoking and colorectal cancer incidence and mortality: Systematic review and meta-analysis. International Journal of Cancer, 124 (10), 2406-2415.
Lynch, S. M., Vrieling, A., Lubin, J. H., Kraft, P., Mendelsohn, J. B., Hartge, P., Stolzenberg-Solomon, R. Z. (2009). Cigarette smoking and pancreatic cancer: A pooled analysis from the pancreatic cancer cohort consortium. American Journal of Epidemiology, 170(4), 403-413.
Brennan, Paul., Bogillor, Olivier., Greiser, Eberhard., cordier, SylvaineBoffeta Paolo. (2000). Cigarette Smoking and Bladder cancer in Men: Analysis of 11 case control studies. Int. J. Cancer, 86, 289–294.
Ko.Ying-Chin., Huang, Li-Yun., Lee, Chien-Hung. (1995). Betel quid chewing, cigarette smoking and alcohol consumption related to oral cancer in Taiwan. Journal of Oral pathology and Medicine, 24, 450-53.
