Development of a risk score for colorectal cancer in men

Colorectal cancer is a common and preventable disease for which screening rates remain unacceptably low.

We developed a risk scoring system for the development of colorectal cancer among participants in the Physician's Health Study, a prospective cohort of 21,581 US male physicians who were all free of cancer. Predictors of colorectal cancer were self-reported and identified from the baseline questionnaire. Logistic regression was used to determine the independent predictors of incident colorectal cancer over the follow-up period. Risk scores were created from the sum of the odds ratios of the final predictors and used to divide the cohort into categories of increasing relative risk.

During 20 years of follow-up, 381 cases of colon cancer and 104 cases of rectal cancer developed in the cohort. Age, alcohol use, smoking status, and body mass index were independent significant predictors of colorectal cancer. The point scores were used to define 10 risk groups. Those in the highest risk group (9-10 points) had an odds ratio of 15.29 (6.19-37.81) for colorectal cancer compared with those with the lowest risk. We further stratified scores into 3 risk classes. Compared with those at the lowest relative risk, the odds ratio for colorectal cancer was 3.07 (2.46-3.83) in the intermediate risk group and 5.75 (4.44-7.44) in the highest risk group.

We developed a simple scoring system for colorectal cancer that identifies men at increased relative risk on the basis of age and modifiable factors. This tool should be validated in other populations.