Computed tomography colonography versus colonoscopy for detection of colorectal cancer: a diagnostic performance study

Background Colonoscopy is the reference standard for the detection of colorectal cancer but it is an invasive technique and has the risk of bowel perforation and bleeding. Unlike colonoscopy, sedation is not required in computed tomography colonography and requires additional reassurance endoscopy. The objectives of the study were to compare the diagnostic performance of computed tomography colonography against colonoscopy for a diagnosis of colorectal cancer. Methods Data regarding any polyp >= 10 mm diameter (o) and < 10 mm o but suspicious polyps of computed tomography colonography (n = 318), colonoscopy (n = 318), and surgical pathology (n = 77) for symptomatic colorectal cancer patients were collected and analyzed. Lesion ulceration, extramural invasion, and/ or lesion shouldering was considered as a suspicious polyp. Beneficial scores for decision making of curative surgeries were evaluated for each modality. The cost of diagnosis of colorectal cancer was also evaluated. Results Either of diagnosis showed polyps >= 10 mm o in 27 patients and polyps of 50 patients were < 10 mm o but suspicious. Therefore, a total of 77 patients were subjected to surgery. With respect to surgical pathology, sensitivities for computed tomographic colonography and colonoscopy were 0.961 and 0.831. For detection of >= 10 mm o polyp, benefit score for computed tomographic colonography and colonoscopy were 0-0.906 diagnostic confidence and 0.035-0.5 diagnostic confidence. For polyps, >= 10 mm o but not too many large polyps, colonoscopy had the risk of underdiagnosis. For < 10 mm o but suspicious polyps, < 0.6 mm o and < 2.2 mm polyps could not be detected by computed tomographic colonography and colonoscopy, respectively. The computed tomographic colonography had less cost than colonoscopy (1345 +/- 135 yen / patient vs. 1715 +/- 241 yen / patient, p < 0.0001) for diagnosis of colorectal cancer. Conclusion Computed tomographic colonography would be a non-inferior alternative than colonoscopy for a diagnosis of colorectal cancer.