Colorectal cancer is the third most common form of cancer and the fourth most frequent cause of cancer deaths worldwide.
The association between cigarette smoking and colorectal cancer has been inconsistent among studies.
Dr Edoardo Botteri and colleagues from Italy clarified the association of cigarette smoking and colorectal cancer.
The research team performed a comprehensive literature search and a meta-analysis of observational studies considering both incidence and mortality.
The team performed a literature search using PubMed, ISI Web of Science, and EMBASE to 2008, with no restrictions.
The researchers also reviewed references from all retrieved articles.
All articles were independent and contained the minimum information necessary to estimate the colorectal cancer risk associated with cigarette smoking and a corresponding measure of uncertainty.
Articles were reviewed and data were extracted and cross-checked independently by 3 investigators, and any disagreement was resolved by consensus among all 3.
|The pooled relative risk of 1.2 for ever vs never smokers|
|Journal of the American Medical Association|
The team included 106 observational studies in the analysis of incidence.
The research team found 26 studies that provided adjusted risk estimates for ever smokers vs never smokers, leading to a pooled relative risk of 1.2.
Smoking was associated with an absolute risk increase of 11 cases per 100,000 person-years.
The team found a statistically significant dose-relationship with an increasing number of pack-years and cigarettes per day.
However, the association was statistically significant only after 30 years of smoking.
The research team included 17 cohort studies in the analysis of mortality.
The pooled risk estimate for ever vs never smokers was 1.3.
Smoking was associated with an absolute risk increase of 6 deaths per 100,000 person-years.
For both incidence and mortality, the association was stronger for cancer of the rectum than of the colon.
Dr Botteri’s team comments, “Cigarette smoking is significantly associated with colorectal cancer incidence and mortality.”