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CTC study questions new recommendations
Experts disagree on implications of findings
A new study calls into question some of the recommendations put forth in new guidelines issued by the American Cancer Society, the US Multi-Society Task Force on Colorectal Cancer, and the American College of Radiology (ACR), regarding CT colonography (CTC),1 but there remains considerable disagreement about the implications of the findings.
The study, by Douglas Rex, MD, FASGE, a professor of medicine at Indiana University School of Medicine and director of endoscopy at Indiana University Hospital, both in Indianapolis, looked at two of the document's recommendations:
Rex, who is one of the co-authors of the guidelines, applied these recommendations to an endoscopic database of information regarding more than 10,000 polyps that had been removed and processed over five years. He concluded that if CTC and the ACR guidelines had been used rather than colonoscopy in these patients, then 29% of all patients and 30% of those patients over age 30 with high-risk adenoma findings would have been interpreted as normal.
"The definitions that I used for 'high risk' are not based just on adenomas; they are based on what is called 'high-risk adenoma findings': the presence of three or more small adenomas or three or more adenomas of any size," explains Rex. "In our post-polypectomy studies, that has been the most consistent predictor that within the next few years a person is going to present with an advanced adenoma." Other high-risk findings, according to current post-polypectomy surveillance guidelines, include any adenoma that is 1 cm or larger, or any adenoma with high-grade dysplasia or villous elements.
However, Perry J. Pickhardt, MD, an associate professor of radiology at the University of Wisconsin Medical School in Madison and also a co-author of the guidelines, suggests that Rex's findings are driven by the false premise that three or more diminutive adenomas (5mm and smaller) are, in fact, a high-risk finding. Such a premise, he says, turns the logic of colorectal cancer screening upside down.
"CTC seems to be slightly more sensitive [than colonoscopy] for clinically relevant lesions, particularly the all-important large polyps," Pickhardt says.
However, Rex also is concerned about the ACR's contention that patients don't necessarily need to know if they have three or more smaller polyps. "I am not sure it is even ethical not to tell the patient, "he says. "If you see several polyps that you think are definitely there, even if they are small, I think the patient at least deserves to know that and to not have the study reported as normal."
Further, Rex is uncomfortable with ACR's position that a patient who has 1-2 polyps that are 6 mm to 9 mm in size can simply have a repeat CTC in three years. "I would rather those patients be offered colonoscopy and polypectomy to have those polyps removed," he says.
Rex acknowledges that not much is known at this point about the natural history of small adenomas. However, Pickhardt indicates that he is involved with just such a study that is under way. "It will likely show that small polyps are completely benign and need not be aggressively pursued with invasive tests," he says.