People who have had risky, possibly pre-cancerous polyps removed from their colon may be able to wait up to five years until their next colonoscopy, a new study from Germany suggests.

Recommendations from the American Cancer Society and other organizations call for a follow-up colonoscopy three years after large or risky adenomas are removed to check for further signs of cancer.

Extending that timeframe to five years may mean more colonoscopies could be done in people who really need them - such as older adults who’ve never been screened for colon cancer, researchers wrote Monday in the Journal of Clinical Oncology. The procedures run about $1,000.

But researchers not involved in the new study argued that it’s too early to loosen the timeline for follow-up colon exams.

“Patients with high-risk polyps are at increased risk for developing colon cancer and their tumors may grow faster,” said Dr. Benjamin Lebwohl, who studies colon cancer screening at Columbia University Medical Center in New York.

“This study provides a measure of reassurance to patients and gastroenterologists,” he told Reuters Health. “It appears that those patients with high-risk polyps were similarly protected against colon cancer even beyond the three-year interval.”

Still, “I think it’s premature to interpret these results as saying that we can relax all intervals,” Lebwohl said.

For the new study, Dr. Hermann Brenner of the German Cancer Research Center in Heidelberg and his colleagues compared 2,600 patients with colon cancer - including 160 who’d had colon polyps removed in the last decade - with 1,800 similar people without cancer, 264 of whom had a history of adenoma removal.

As expected, the researchers found that having risky polyps taken out in the last three years was tied to a lower chance of colon cancer: Those patients were 60 percent less likely to be diagnosed with cancer than people who hadn’t had a previous colonoscopy.

And the benefits of prior screening and polyp removal held up for people who’d had the procedure three to five years ago, and had half the risk of cancer as their unscreened peers.

The findings were consistent for men and women as well as both younger and older patients, the researchers reported.

Brenner and his colleagues concluded that “extension of surveillance intervals to five years should be considered, even after detection and removal of high-risk polyps.”

In people who haven’t had polyps found before, the U.S. Preventive Services Task Force recommends screening for colon cancer using colonoscopy every 10 years, or with other methods more frequently. That guideline from the government-backed panel applies to people age 50 to 75.

“There’s no question colonoscopy prevents colon cancer - this is very much a matter of how to fine-tune this effective tool,” Lebwohl said.

Dr. Gregory Cooper, a gastroenterologist from University Hospitals Case Medical Center in Cleveland, Ohio, agreed with Lebwohl that the results should be interpreted with caution.

He noted that the researchers looked back at patient records to compare those with or without colon cancer, rather than tracking cancer-free patients forward and seeing who got the disease, which is considered a more reliable technique.

“I wouldn’t necessarily change practice based on this paper,” Cooper, who also wasn’t tied to the new study, told Reuters Health.

“Until we have better evidence, the interval should stay at three years for the high-risk (patients),” he said.

After a colonoscopy, Cooper added, it’s not always clear to patients what they should be doing in terms of follow-up.

So people who had polyps removed during their procedure should make sure to have a discussion with their primary care doctor or the person who did the colonoscopy about when they’re due back, he advised.

SOURCE: Journal of Clinical Oncology, online July 23, 2012.

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