NEW YORK (Reuters Health) – Information from previous colonoscopies may help identify low-risk polypectomy patients who are unlikely to benefit from intense surveillance, a large prospective cohort study indicates.

Most studies of postpolypectomy surveillance have used a patient’s most recent colonoscopy to determine surveillance intervals, Dr. Douglas J. Robertson from the Veterans Affairs Medical Center in White River Junction, Vermont, and co-authors note in the Annals of Internal Medicine for July 21.

However, they suggest, “A risk profile based on multiple examinations might better delineate high- and low-risk patients than a single examination.”

To estimate the risk for adenoma recurrence on a third examination, based on results from 2 previous colonoscopies, Dr. Robertson’s group analyzed data from a subset of participants in the Aspirin/Folate Polyp Prevention Study.

All 564 subjects had a first large-bowel adenoma found and removed during baseline colonoscopy at study entry. A second examination was conducted about 3 years later, again with removal of all detected polyps, and a third exam was done either 3 or 5 years after the second. (Patients with cancers found at or before the second exam were not included.)

“Advanced adenomas” were 1 cm or larger, with tubulovillous or villous histologic features or high-grade dysplasia. “High-risk findings” consisted of at least 3 adenomas or at least 1 advanced adenoma.

At the third examination, 10.3% of subjects had high-risk findings, the report indicates, with risk varying substantially depending on the results of past endoscopies.

At the third exam, high-risk findings were found in 5.0% of patients with low-risk findings on the first two colonoscopies, 18.2% of patients with high-risk adenomas on both previous colonoscopies, 19.0% of patients with low-risk baseline examination and high-risk adenomas at the second exam, and 12.3% of those with high risk findings at baseline and no adenomas on the second.

Given that “relatively few participants…with low-risk findings on their first 2 examinations had high-risk results on their third colonoscopy….a longer follow-up interval may be appropriate for this…much larger group,” the researchers said.

“Our results,” the investigators conclude, “may provide clinicians with a rationale to suggest a 10-year surveillance interval in this lowest-risk group. Of course, other clinical factors (for example, preparation quality) may also determine the correct interval.”

Reference:
Ann Intern Med 2009;151:103-109.