Background: Individualizing recommendations for colorectal cancer (CRC) screening intervals and modalities requires accurate risk assessment. Although hereditary predisposition is commonly used, the effect of exogenous risk factors has remained largely unexplored. To address this, we analyzed the age at presentation and location of CRC in relation to alcohol and tobacco use. Methods: We queried the IMPAC Medical Registry Services Cancer Information Resource File for CRCs diagnosed between June 1, 1993, and December 31, 2003. Subjects were classified as current, past, or never users of alcohol and tobacco. A logistic regression model for location of CRC and a linear regression model for age at diagnosis were constructed using these explanatory variables along with gender, race, and insurance status. Results: Our data set consisted of 161 172 patients with CRC. Current drinking, smoking, and smoking plus
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