In a large population-based study, investigators found that colonoscopy significantly decreased the absolute risk of colorectal cancer (CRC) and that the risk of CRC can be further reduced by adherence to a healthy lifestyle, regardless of the risk due to genetic factors.  These study findings were published in Gastroenterology.

Carr and colleagues leveraged data from a population-based, case-control study in Germany, the DACHS study, and a population registry.  The team estimated 30-year absolute risk estimates of CRC based on 3 major determinants of CRC risk: a healthy lifestyle score (integrating smoking, alcohol consumption, diet, physical activity, and body mass index), a polygenic risk score (based on 90 single nucleotide polymorphisms), and colonoscopy history.

Data from 4220 patients with CRC and 3338 participants without CRC who were recruited from 2003 to 2016 were included in the analysis. Overall, the mean age of all participants was 68.4 years (men, 61.5%; women, 38.5%). The analysis stratified the data by patient sex and age.


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History of colonoscopy was the strongest preventive factor. Men and women who had colonoscopy in the preceding 10 years had a reduced relative risk of CRC compared with men and women who did not have colonoscopy (odds ratio [OR], 0.34; 95% CI, 0.30-0.39 and 0.38; 95% CI, 0.32-0.44, respectively).

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Men and women who adhered to a healthy lifestyle in the preceding 10 years had a reduced relative risk of CRC compared with men and women who maintained unfavorable lifestyles (OR, 0.55; 95% CI, 0.47-0.64 and 0.50; 95% CI, 0.40-0.63, respectively).

The risk for CRC was higher in both men and women with high or intermediate genetic risk scores relative to those with low genetic risk scores (men: OR high, 2.24; 95% CI, 1.93-2.62; OR intermediate, 1.54; 95% CI, 1.32-1.80 and women: OR high, 2.23; 95% CI, 1.84-2.70; OR intermediate, 1.45; 95% CI, 1.19-1.77).

Focusing on 50-year-old men and women, the absolute risk of CRC varied according to the polygenic risk score and the healthy lifestyle score in participants without colonoscopy (men, 3.5%-13.4% and women, 2.5%-10.6%) and with colonoscopy (men, 1.2%-4.8% and women, 0.9%-4.2%).

Among all of the risk factor profiles, the authors highlighted that the 30-year absolute risk estimates for both men and women consistently decreased with adherence to a healthy lifestyle.

Limitations of the study included treating the lifestyle factors as fixed variables (thus the authors could not assess changes in the absolute risk of CRC with change in lifestyle choices), that the data were solely from the German population (limiting generalizability), and self-reporting of lifestyle information may have resulted in under/overreporting for some variables comprising the healthy lifestyle score.

“These findings highlight the strong protective effect of colonoscopy and the potential of lifestyle interventions to reduce the risk of CRC across the population, even among those at high genetic risk of CRC and still among those who have had a colonoscopy,” wrote the authors. “Our absolute risk estimates can be useful to facilitate communication and to better inform the public about the magnitude, potentials and limits of CRC prevention.”

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Reference

Carr PR, Weigl K, Edelmann D, et al. Estimation of absolute risk of colorectal cancer based on healthy lifestyle, genetic risk, and colonoscopy status in a population-based study [published online March 14, 2020]. Gastroenterology. doi:10.1053/j.gastro.2020.03.016