Background: Colonoscopy has a reported localization error rate as high as 21% in detecting colorectal neoplasms. Preoperative repeat endoscopy has been shown to be protective against localization errors. There is a paucity of literature assessing the utility of staging computerized tomography (CT) and repeat endoscopy as diagnostic tools for detecting localization errors following initial endoscopy. The objective of this study is to determine the diagnostic characteristics of staging CT and repeat endoscopy in correcting localization errors at initial endoscopy.
Methods: A retrospective cohort study was conducted at a large tertiary academic center between January 2006 and August 2014. All patients undergoing surgical resection for CRC were identified. Group comparisons were conducted between (1) patients that underwent only staging CT (staging CT group), and (2) patients that underwent staging CT and repeat endoscopy (repeat endoscopy group). The primary outcome was localization error correction rate for errors at initial endoscopy.
Results: 594 patients were identified, 196 (33.0%) in the repeat endoscopy group, and 398 (77.0%) patients in the staging CT group. Error rates for each modality were as follows: initial endoscopy 8.8% (95% CI 6.5-11.0), staging CT 9.3% (95% CI 6.5-11.0), and repeat endoscopy 2.6% (95% CI 0.3-4.7); p < 0.01. Repeat endoscopy was superior to staging CT in correcting localization errors for left-sided / rectal lesions (81.2% vs. 33.3%; p < 0.01), right-sided lesions (80.0% vs. 54.5%; p = 0.21), and overall lesions (80.8% vs. 42.3%; p < 0.01). Repeat endoscopy compared to staging CT demonstrated relative risk reduction of 66.7% (95% CI 22-86%), absolute risk reduction of 38.5% (95% CI 14.2-62.8%), and odds ratio of 0.18 (95% CI 0.05-0.61) for correcting errors at initial endoscopy.
Conclusions: Repeat endoscopy in colorectal cancer is superior to staging CT as a diagnostic tool for correcting localization-based errors at initial endoscopy.
Keywords: Accuracy; Colonoscopy; Colorectal cancer; Computerized axial tomography; Endoscopy; Tumor localization.