Diminutive polyps not likely to become cancerous.
NEW ORLEANS -- Diminutive polyps have a very low risk of advanced histology and virtually no risk of cancer, and therefore clinicians should balance the small potential benefit of removing them against potential harms posed by polypectomy, Dr. Thomas F. Imperiale said.
In an invited lecture on the management of diminutive polyps, Dr. Imperiale acknowledged that endoscopists often elect to remove these polyps, but he said they should consider several factors first.
Diminutive polyps (less than or equal to 5 mm) constitute at least 80% of all colorectal polyps and have been identified in 44% of persons undergoing colonoscopy for any indication, he said.
Nearly half occur in the sigmoid colon and rectum, and the remainder are fairly evenly distributed throughout the colon. Diminutive polyps are neoplastic in 35%-50% of cases, with the risk of neoplasia increasing in accordance with polyp size. The highest risk occurs in the ascending colon and cecum, said Dr. Imperiale, professor of medicine, Indiana University Medical Center, Indianapolis.
The clinical importance of diminutive polyps is not great, as cancer is uncommon (less than 1%). In a recent systematic review of four studies involving more than 20,000 patients, the frequency of advanced lesions among patients whose largest polyp was diminutive was 0.9%, but it rose dramatically to 73.5% when the polyp was 10 mm or larger (Aliment. Pharmacol. Ther. 2010;31:210-7).
Furthermore, these lesions grow slowly, generally less than 0.5 mm per year. Hyperplastic polyps appear to have an even slower rate of growth, he added.
Like the cancer risk, the benefit of removing polyps is proportional to their size. The number needed to resect to prevent one advanced adenoma or colorectal cancer, therefore, varies widely.
"The prevention of one cancer in a person with a diminutive polyp is associated with a cost-effectiveness ratio that is 5-10 times the established cost-effectiveness threshold," he pointed out. "For large polyps, however, resection is cost saving."
Polypectomy is probably overutilized for diminutive polyps and conveys more harm than benefit, he maintained, noting that it increases the risk for major complication and, when incompletely performed, is responsible for 30% of interval cancers.
In vivo histologic assessment has a potential role in the management of diminutive polyps. With this, the clinician can avoid removing non-neoplastic polyps, especially distal ones, thus reducing costs and risks; can resect and discard small adenomas, reducing pathology costs; and can identify cancer via real-time histology, which improves treatment selection, Dr. Imperiale said.
Although in vivo histology could be used to avoid the removal of non-neoplastic polyps, it also means that adenomas are left intact and the surveillance interval could prove to be too long (which raises the risk of cancer) or too short (which increases risk from needless polypectomy), he said.
Several recent studies have evaluated the effect of optical diagnosis without pathology on surveillance intervals, essentially concluding that adenomatous and hyperplastic polyps can be adequately identified and that this approach might be acceptable for diminutive targets.
Before such techniques are implemented, he said, "we need more realtime data. We need to identify optimal techniques. And we need to quantify the effects on surveillance and estimate the downstream effects, which would be the incidence of colorectal cancer, complications, and costs."
Disclosures: Dr. Imperiale has no relevant financial disclosures.
FROM THE ANNUAL DIGESTIVE DISEASE WEEK