A pooled analysis of smoking and colorectal cancer: timing of exposure and interactions with environmental factors
A partir des données de 8 études (6 796 cas et 7 770 témoins), cette analyse fait le point sur l'association entre le tabagisme et le risque de cancer colorectal, en fonction de la durée d'exposition et d'autres facteurs environnementaux
Background:Considerable evidence suggests that cigarette smoking is associated with a higher risk of colorectal cancer. What is unclear, however, is the impact of quitting smoking on risk attenuation and whether other risk factors for colorectal cancer modify this association. Methods:We performed a pooled analysis of 8 studies, including 6,796 colorectal cancer cases and 7,770 controls to evaluate the association between cigarette smoking history and colorectal cancer risk, and to investigate potential effect modification by other risk factors. Results:Current smokers (OR=1.26, 95% CI=1.11-1.43) and former smokers (OR=1.18, 95% CI=1.09-1.27), relative to never smokers, showed higher risks of colorectal cancer. Former smokers remained at higher colorectal cancer risk, relative to never smokers, for up to about 25 years after quitting. The impact of time since quitting varied by cancer subsite: the excess risk due to smoking decreased immediately after quitting for proximal colon and rectal cancer, but not until about 20 years post-quitting for distal colon cancer. Further, we observed borderline statistically significant additive interactions between smoking status and BMI (relative excess risk due to interaction [RERI]=0.15, 95% CI:-0.01-0.31, P=0.06) and significant additive interaction between smoking status and fruit consumption (RERI=0.16, 95% CI: 0.01-0.30, P=0.04). Conclusions:Colorectal cancer risk remained increased for about 25 years after quitting smoking, and the pattern of decline in risk varied by cancer subsite. BMI and fruit intake modified the risk associated with smoking. Impact:These results contribute to a better understanding of the mechanisms through which smoking impacts colorectal cancer etiology.