Department of Radiation Oncology, University of Rochester Medical Center
Introduction
A 2010 article studies how second-hand smoke (SHS) from active cigarette smoking impacts colorectal cancer. Past studies have failed to find a link between smoking and colorectal cancer. Therefore, this study is significant because researchers determine an association between SHS and colorectal cancer, finding that long-term cigarette smoking is linked with increased colorectal cancer risk in males, but not in females. Although other studies may report an increased risk in individuals with long-term smoking exposure, not all support an association between smoking and colorectal cancer.
Methods
Subjects included 1,203 males and females, from 40 to 88 years of age. All subjects were patients with colorectal cancer, at Roswell Park Cancer Institute between 1982 and 1998. The control group included 2,406 individuals free of any neoplasm ranging in age from 40 to 86. SHS exposure was determined by comparing the odds ratios for each smoking variable in the sample and for those who said they had no SHS exposure (Peppone et al., 2010).
Results
Please click the following graphs for a clearer view.
Table 1 displays sociodemographic, lifestyle, and dietary variables of the controls. Cases and controls are alike in age, gender, education, income, alcohol consumption, fruit consumption, and vegetable consumption. Conversely, they are much more likely to have a higher BMI, live outside Western New York (WNY), be non-Caucasian, have a relative previously diagnosed with CRC, consume less cruciferous vegetables, consume more meat, and take less aspirin (Peppone et al., 2010).
Interestingly, Table 2 shows odds ratios which illustrate that there was no increase in colorectal cancer odds for females with the highest exposures of SHS.
Table 3 shows odds ratios which illustrate an increase in colorectal cancer odds for males who smoked more than 1 pack a day, smoked 46 or more pack-years, and smoked 20 or more pack-years before the age of 30. Colorectal cancer odds are more than doubled when compared to non-smokers with no secondhand smoke exposure. But the significant increase in colorectal cancer odds was noted for heavy, long-term smoking males when not accounting for SHS exposure (Peppone et al., 2010).
Discussion
The results show no increased risk of colorectal cancer in non-smoking females with exposure to seven or more hours a day of SHS. However, there seems to be a 58% increased risk in odds for non-smoking males exposed to seven or more hours of SHS everyday (Peppone et al., 2010). This may be because there were less females in the study, with a heavy smoking history. Limitations of this study include dishonesty in the questionnaires about SHS exposure. However, SHS exposure was assessed solely for the current frame in time, and not throughout adulthood (Peppone et al., 2010). Therefore, assessments may underestimate SHS exposure. Overall, further research will determine a direct association between SHS and colorectal cancer risk.
Conclusion
In this study, SHS exposure leads to an increased risk of colorectal cancer for all smoking variables. This is significant because this study proves that future studies must account for SHS exposure when determining a link between smoking and colorectal cancer.
References
Peppone L.J., Reid, M.E., Moysich, K.B., Morrow, G.R., Jean-Pierre, P., Mohile, S.G., Darling, T.V., Hyland, A. (2010). The effect of secondhand smoke exposure on the association between active cigarette smoking and colorectal cancer. Cancer Causes and Control, 21(8), 1247-1255.
