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Colonoscopy remains gold standard in cancer detection

DURHAM, NORTH CAROLINA. The prognosis for colorectal cancer is good if caught early before it spreads to other organs, so screening for early detection and treatment are essential to increase survival rates. Currently, screening methods for colorectal cancer include colonoscopy, air contrast barium enema (ACBE), and in recent years, computed tomographic colonography (CTC).

During a colonoscopy, physicians are able to remove small samples of tissue or polyps for laboratory tests, whereas this is not possible using a virtual colonoscopy with a scanner, such as CTC. The ACBE method uses barium (a liquid which shows up on x-rays) placed into the colon through an enema procedure. Researchers from Duke University Medical Center aimed to directly compare these different types of screening in order to determine the most effective method for detecting colon polyps and cancer. They recruited 614 patients who were at high risk for colon abnormalities. Mean age was 57 years and 70 per cent were men. Lesions were found in 179 participants, as determined by the combined results of the three tests.

ACBE was found to be have a sensitivity of 48 per cent for lesions 10 millimeters or larger, CTC 59 per cent, and colonoscopy 98 per cent. For lesions of 6-9 mm, ACBE was 35 per cent sensitive, CTC 51 per cent, and 99 per cent for colonoscopy. The authors also explain that for lesions of 10 mm or larger, the specificity was greater for colonoscopy than for ACBE or CTC. They conclude that colonoscopy is the most effective method and suggest that the results are important for the diagnostic use of colon imaging tests.

Previous estimates of the sensitivity of CTC for detecting colon polyps and cancers have varied widely. A recent study found CTC performance was much more impressive than in the current study, and researchers expect that improved technology and greater examiner experience are likely to increase the accuracy of CTC over time.
Rockey, D C et al. Analysis of air contrast barium enema, computed tomographic colonography, and colonoscopy: prospective comparison. Lancet, Vol. 365, January 2005, pp305-11

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