The National CT Colonography Trial

OBJECTIVES: Primary * Compare the sensitivity of computed tomographic colonography (CTC) vs colonoscopy for detecting significantly large lesions (≥ 10 mm in diameter) in asymptomatic participants, in terms of specificity, area under the ROC curve, and predictive values for detecting clinically significant colorectal neoplasia. Secondary * Determine the interobserver variation in accuracy of interpreting CTC examinations of these participants, including any benefits of a primary 3-dimensional read and/or independent second interpretations. * Determine the effects of different colon preparations on the accuracy of CTC in these participants. * Compare participant acceptance and willingness to have a repeat examination by CTC vs colonoscopy. * Determine the accuracy of CTC in detecting flat lesions in the colon of these participants. OUTLINE: This is a multicenter study. Participants receive an oral laxative, oral bisacodyl, and three doses of oral barium sulphate 24 hours before imaging. After cathartic cleansing, participants undergo computed tomographic colonography followed by colonoscopy. Participants are followed up for approximately 4 weeks. PROJECTED ACCRUAL: A total of 2,607 participants will be accrued for this study.