Long-Term Colorectal Cancer Mortality after Adenoma Removal

Published - Written by Daniela Lamas

Your patient had thought it would be a relief to get the colonoscopy over with. “Not for another ten years,” she had vowed as she chugged that dreaded colonoscopy prep.

But then there was a polyp – low-risk, she was told – but with it, recommendations to return for another colonoscopy in as few as three years. She returned to your office, relieved that a potential malignancy had been caught early but very concerned by the recommendation to intensify her screening. Does the now-excised polyp place her at higher risk of dying from colon cancer?

In all that’s been written recently on colon cancer screening, her question – that is, whether or not polyp surveillance colonoscopies reduce colon cancer mortality – has remained unanswered. Our current screening guidelines aren’t based on data about mortality and colon cancer incidence after the removal of high and low-risk adenomas.

Now, results published in this week’s issue of the Journal offer new evidence about the outcomes of high and low-risk adenoma patients, that might ultimately change these recommendations.

Using population-based data from a cancer registry in Norway, Magnus Loberg and colleagues tracked colon cancer mortality of patients who’d had adenomas removed between 1993 and 2007.  They identified 40,826 such patients, and followed them for an average of 7.7 years. Of note, in Norway, guidelines recommend that patients who are found to have high-risk adenomas undergo repeat colonoscopy in 10 years, and in 5 years if they have multiple adenomas. In contrast to guidelines in the US, those with low-risk adenomas require no additional screening.  They compared the incidence of newly diagnosed colon cancer and mortality in these patients to the general population.

What they found was surprising, given our current screening recommendations.

Those who’d had what the authors defined as low-risk adenomas excised actually had a 25% lower risk of death than the general population. In contrast, those with high-risk adenomas experienced a higher rate of colon cancer mortality than the general population – despite these adenomas having been removed.

In an accompanying editorial, David Lieberman, who heads the Oregon Health and Science University’s division of gastroenterology, notes that there are many potential reasons for the colon cancer deaths seen in the high-risk adenoma patients. The polyps might have been incompletely removed. The patients might have had other adenomas that were missed at colonoscopy, or a genetic predisposition to develop such adenomas. He notes that the study doesn’t include information about the quality of these colonoscopies that could help to understand the reasons behind this difference – regardless, he writes, these findings “provide justification for surveillance in patients with high-risk adenomas.”
But what about those with low-risk adenomas, who didn’t receive any additional screening in Loberg’s study and experienced lower rates of colon cancer nonetheless? Leiberman notes that there might exist a low-risk group of patients for whom close surveillance is not necessary. While further study is needed before making this determination, Lieberman writes, “This would be an exciting development for patients and health care systems.”

For your patient, the results are reassuring, but they don’t change practice. She’ll still get that colonoscopy, while researchers continue to work to determine who does and who doesn’t benefit from surveillance colonos.