Despite advances in the accuracy of CT colonography in detecting polyps, digestive health experts urge patients to consider risks and realities

Tuesday, 30 November 1999 00:00 |

Findings from a trial of CTC compared to colonoscopy in detecting large pre-cancerous polyps raise important issues for the public about colorectal cancer screening.

Findings from a trial of the accuracy of CT colonography (CTC) compared to complete colonoscopy in detecting large pre-cancerous polyps and colorectal cancers, coordinated by the American College of Radiology Imaging Network (ACRIN), raise several important issues for the public about colorectal cancer screening using a CT scan of the abdomen: the potential need for follow-up with complete colonoscopy in many cases, the real risk of undetected and unreported smaller growths with pre-cancerous potential, the reality of radiation risks relating to CT scans, as well as questions regarding patient acceptability of this test.

"Today's findings underscore the reality that many patients who have polyps detected by CT colonography will still have to undergo complete colonoscopy," explained Dr. Amy Foxx-Orenstein, DO, FACG, President of the American College of Gastroenterology. Researchers found that as many as 12 per cent to 17 per cent of study participants screened by CTC would have to be referred for complete colonoscopy depending on the size threshold for reporting lesions in the colon. Of more significant concern, is that the researchers only reported growths in the colon 5 mm or larger, leaving unreported and therefore undetected an untold number of potentially high risk pre-cancerous growths.

"The College sees significant strengths in the proven benefits of visualizing pre-cancerous growths and removing them in a single examination during colonoscopy," commented Dr. Foxx-Orenstein.

"There is a tremendous body of evidence that shows that clearing the colon of polyps, including small polyps, significantly reduces colorectal cancer mortality. Because of its excellent sensitivity in detecting polyps and its potential for removing them and breaking the sequence of polyp to cancer in a single diagnostic and therapeutic intervention, complete colonoscopy is one of the most powerful preventive tools in clinical medicine. Until a radiographic test can meet that standard, gastroenterologists will continue to champion the lifesaving potential of colonoscopy," Foxx-Orenstein added.