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Serrated polyps plus high-risk adenomas increase colon cancer risk
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ORLANDO — Individuals in whom colonoscopy revealed both serrated colon polyps and high-risk adenomas showed a significantly higher risk for developing future high-risk adenomas, and may therefore have an increased risk for colorectal cancer than those with high-risk adenomas alone, according to research presented at the World Congress of Gastroenterology at ACG 2017.
These findings, which researchers also recently published in detail in Gastroenterology, suggest that patients with both serrated polyps (SPs) and high-risk adenomas (HRAs) may benefit from closer surveillance.
“We demonstrated that SPs alone do not predict conventional HRAs,” Joseph C. Anderson, MD, MHCDS, of White River Junction Veterans Affairs Medical Center and Dartmouth College, said during his presentation. “We also found that [SPs] predict future large SPs, so large SPs rather than conventional [HRAs] may be a better surveillance outcome in patients with index SPs to monitor success. ... Finally, we had a novel finding of showing there is an increased risk of HRA in patients with HRA and [sessile serrated polyps (SSPs)] or [traditional serrated adenomas (TSAs)].”
Because only limited data inform surveillance guidelines for patients with SPs detected on index colonoscopy, Anderson and colleagues evaluated population-based data from the New Hampshire Colonoscopy Registry (NHCR) to determine the risk for metachronous lesions in patients with clinically significant SPs, including large SPs exceeding 1 cm, SSPs or TSAs.
They evaluated data on 4,616 individuals (median age, 59 years; 47.5% men) who underwent two colonoscopies at 28 endoscopy facilities (median time to surveillance, 4.9 years). The absolute risk for metachronous HRA was 6.3%, and absolute risk for metachronous large SP exceeding 1 cm was 1.2%.
Compared with patients in a reference group with normal exams, patients with HRA and synchronous SPs (OR = 5.61; 95% CI, 1.72-18.28), those with HRAs and synchronous SSPs or TSAs (OR = 16.04; 95% CI, 6.95-37) and those with HRAs alone (OR = 3.86; 95% CI, 2.77-5.39) on index colonoscopy showed an increased risk for metachronous HRAs. Further, those with only large SPs (OR = 14.34; 95% CI, 5.03-40.86) or SSPs or TSAs (OR = 9.7; 95% CI, 3.63-25.92) at index colonoscopy showed an increased risk for large metachronous SPs.
“We have identified a subgroup of individuals with both high-risk adenomas and serrated polyps who may need more intense surveillance such as increased frequency of colonoscopies,” Anderson said in a press release. “We also observed that having serrated polyps on index exam is associated with an increased risk for future serrated polyps but not high-risk adenomas. Examining rates of serrated polyps rather than high-risk adenomas on follow-up colonoscopy may be the best way to monitor the success of surveillance in people with serrated polyps.”
One of the strengths of this study is the large size, thoroughness and longitudinal nature of the NHCR registry, which has collected comprehensive data on more than 150,000 colonoscopies across New Hampshire since 2004, according to the press release.
“We follow patients at each successive colonoscopy and can examine the risk that patients can have for future polyps based on an index exam,” Anderson said in the press release. “The NHCR provided data for a large group of individuals who had both an index and follow-up colonoscopy allowing us to address the important clinical question of risk for people with serrated polyps.”
Anderson and colleagues plan to further study risk factors and genetic mutations that can help identify individuals at risk for both serrated polyps and high-risk adenomas, who may therefore be at an increased risk for colorectal cancer, according to the press release.
A poster being presented at the meeting showed “that smoking is a particularly high-risk factor for both these groups,” he noted during his presentation. – by Adam Leitenberger
References:
Anderson JC, et al. Abstract 1. Presented at: World Congress of Gastroenterology at American College of Gastroenterology Annual Scientific Meeting; Oct. 13-18, 2017; Orlando, FL.
Anderson JC, et al. Gastroenterol. 2017;doi:10.1053/j.gastro.2017.09.011.
Disclosures: The researchers report no relevant financial disclosures.
Editor's note: This article was updated on October 30 with clarifications from the study author.Perspective
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Carol Burke, MD
For clinical practitioners, we know that colon cancer develops both from adenomatous polyps, but also from sessile serrated polyps, and the sessile serrated polyps are really a new kid on the block. We’ve learned about them since 2005, so a little bit over a decade. We know that they’re hard to detect, they live on the right side of the colon, and they’re frequently a cause for interval cancers, so there’s been a real push in the medical community, and in gastroenterology in particular, to be able to identify sessile serrated polyps, remove them completely, and decrease the rates of cancer developing for individuals [in whom] they haven’t been detected and completely removed.
[This study] took a look at the risk at having follow-up polyps based on the initial histology of baseline polyps. What the study actually found was that individuals who had high-risk adenomatous polyps at baseline were more likely to have high-risk adenomatous polyps when they were followed up over time, and when individuals had high-risk sessile serrated polyps or serrated polyps, which are big serrated polyps at baseline, they were more likely to have high-risk serrated polyps on follow-up.
We know that there are biological differences between those pathways, where adenomas follow a chromosomal instability pathway, and serrated polyps follow a CpG island methylation pathway, so it’s interesting that [this] data confirms some of my previous data, that if you’re an adenoma former you are likely to form adenomas going forward, and if you’re a serrated polyp former, you’re more likely to [form] serrated polyps.
What they did find was that individuals who have high-risk adenomas at baseline and high-risk serrated polyps at baseline were at very high risk for having high-risk serrated polyps at follow-up, and I think clinically this is quite important. We need to not only think about the surveillance of individuals with adenomas, but get the evidence to support the surveillance colonoscopy for individuals with serrated polyps.
I think what wasn’t defined in the study today is if you have an individual who has high-risk adenomas and has high-risk serrated polyps, do we want to follow them at a shorter time — less than 3 years — than individuals who have only a high-risk adenoma or high-risk serrated polyps? The guidelines are silent on this issue and I think [these data] will help us inform the guidelines as we move forward.
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