CT Colonography Reporting and Data System (C-RADS): Benchmark Values From a Clinical Screening Program

OBJECTIVE. The CT Colonography Reporting and Data System (C-RADS) is a well-recognized standard for reporting findings at CT colonography (CTC). However, few data on benchmark values for clinical performance have been published to date, especially for screening. The purpose of this study was to establish baseline C-RADS values for CTC screening. SUBJECTS AND METHODS. From 2005 to 2011, 6769 asymptomatic adults (3110 men and 3659 women) 50-79 years old (mean [+/- SD] age, 56.7 +/- 6.1 years) were enrolled for first-time CTC screening at a single center. CTC results were prospectively classified according to C-RADS for both colorectal and extracolonic findings. C-RADS classification rates and outcomes for positive patients were analyzed. RESULTS. C-RADS classification rates for colorectal evaluation were C0 (0.7%), C1 (85.0%), C2 (8.6%), C3 (5.2%), and C4 (0.6%). Overall, 14.3% of subjects were positive (C2-C4), and positive findings were more frequent among men (17.5%) than women (11.6%; p < 0.0001). Positivity also increased with age, from 13.4% of patients 50-64 years old to 21.8% of patients 65-79 years old (p < 0.0001). Regarding extracolonic evaluation, 86.6% of patients were either negative for extracolonic findings or had unimportant extracolonic findings (E1 or E2). Likely unimportant but indeterminate extracolonic findings where further workup might be indicated (E3) were found in 11.3% of patients, whereas 2.1% had likely important extracolonic findings (E4). Overall, E3 and E4 rates were increased for older (p < 0.0001) and female (p = 0.008) cohorts. CONCLUSION. C-RADS results from our initial experience with CTC screening may serve as an initial benchmark for program comparison and quality assurance measures.