NEW YORK (Reuters Health) - The results of a new study support the 2006 consensus guidelines for monitoring patients with a known increased risk of colon cancer. The guidelines recommend that a colonoscopy be performed 3 years after removal of three or more small adenomatous polyps - the type likely to develop into cancer -- or one advanced adenoma.

The study, reported Sunday at the 100th annual meeting of the American Association for Cancer Research in Los Angeles, also found that three other factors -- age over 65, male gender, and obesity -- independently raise the risk of polyp recurrence.

In a telephone interview, study presenter Dr. Adeyinka O. Laiyemo, a cancer prevention fellow at the National Cancer Institute in Bethesda, Maryland, noted that repeat colonoscopies make up a significant portion of endoscopic practices. The current findings could help physicians further stratify patients at greatest need for follow-up colonoscopies.

A colonoscopy is a diagnostic test that involves insertion of a lighted flexible tube with a small camera on the end into the bowel, which can detect polyps and colorectal cancer. For patients without risk factors, such as a family history, physicians recommend having a colonoscopy by the age of 50. If the results are normal, it should be repeated after 5 years.

Laiyemo and colleagues examined the diet, lifestyle and polyp characteristics that may be associated with recurrence of a high-risk adenoma during the follow-up colonoscopy among participants in the Polyp Prevention Trial.

Of more than 1,900 patients who had at least one adenoma removed during their first colonoscopy, 230 (12.1 percent) had a high-risk adenoma recurrence and 524 (27.5 percent) had a low-risk adenoma recurrence when they were "re-scoped."

Further analysis indicated that having three or more polyps detected during the first procedure was associated with a 2.5-fold greater likelihood of high-risk adenoma recurrence. "This tells us that the guidelines do predict those patients who are likely to develop high-risk polyps later," Laiyemo said.

Age older than 65, male gender and obesity also increased the risk of high-risk polyp recurrence by 6 percent, 76 percent, and 55 percent, respectively.

"Individuals who fit the high-risk profile should be targeted more closely for lifestyle factor modification and be given high priority for surveillance colonoscopy," Laiyemo and colleagues recommend in meeting materials.

In support of prior studies, the use of non-steroidal anti-inflammatory (NSAID) analgesic drugs, such as ibuprofen and naproxen, was associated with a statistically significant lower risk of polyp recurrence. "NSAID use reduces the risk of polyp recurrence by about 30 percent; however, we know that these drugs are not recommended for use for polyp prevention because of side effects," the researchers note.