LAUSR

Identifying risk factors for early onset colorectal cancer (EOCRC) could help reverse its rising incidence through risk factor reduction and/or early screening. We sought to identify EOCRC risk factors that could be used for decisions about early screening. Using electronic databases and medical record review, we compared male veterans aged 35-49 years diagnosed with sporadic EOCRC (2008-2015) matched 1:4 to clinic and colonoscopy controls without CRC, excluding those with established inflammatory bowel disease, high-risk polyposis and non-polyposis syndromes, prior bowel resection, and high-risk family history. We ascertained sociodemographic and lifestyle factors, family and personal medical history, physical measures, vital signs, medications, and laboratory values 6-18 months prior to case diagnosis. In the derivation cohort (75% of the total sample), univariate and multivariate logistic regression models were used to derive a full model and a more parsimonious model. Both models were tested using a validation cohort. Among 600 cases of sporadic EOCRC (mean [SD] age 45.2 [3.5] years; 66% White), 1200 primary care clinic controls (43.4 [4.2] years; 68% White), and 1200 colonoscopy controls (44.7 [3.8] years; 63% White), independent risk factors included age, cohabitation and employment status, BMI, comorbidity, CRC or other visceral cancer in a first- or second-degree relative; alcohol use; exercise; hyperlipidemia; use of statins, NSAIDs, and multivitamins. Validation c-statistics were 0.75-0.76 for the full model and 0.74-0.75 for the parsimonious model, respectively. These independent risk factors for EOCRC may identify veterans for whom CRC screening prior to age 45 or 50 years should be considered.