Patients with proximal 5 to 9 mm hyperplastic polyps (HPs) are at significantly elevated risk for metachronous large serrated polyps (SPs), according to study data published in Gastrointestinal Endoscopy. While prior studies have described elevated SP risk in patients with large HPs (≥1 cm), sessile serrated polyps (SSPs), and traditional serrated adenomas (TSAs), this study represents the first effort to quantify risk among patients with smaller HPs.

Researchers enrolled patients in the New Hampshire Colonoscopy Registry who had undergone colonoscopies between 2005 and 2018. Patients with at least 1 SP or conventional adenoma detected at index examination as well as a surveillance examination performed at least 12 months after index were eligible for inclusion. The primary outcomes were absolute and adjusted risk for metachronous large (≥1 cm) SPs and advanced adenomas at surveillance examination, estimated with logistic regression. Advanced adenomas were defined as adenomas ≥1 cm or adenomas with villous elements, high-grade dysplasia, or colorectal cancer (CRC). Individuals were hierarchically stratified by the most significant SP finding at index colonoscopy: (1) large (≥1 cm) HPs or any SSP or TSA; (2) 5-9 mm proximal HPs; (3) nonsignificant HPs (<1 cm in rectosigmoid or <5 mm if proximal to sigmoid); (4) high-risk adenomas (advanced adenomas or ≥3 tubular adenomas of any size) with no SPs; and (5) low-risk adenomas with no SPs. Multivariable logistic regression models were stratified by index findings and adjusted for age, gender, body mass index, history of colorectal polyps before index examination, family history of CRC, and smoking history.

The final cohort comprised 8560 patients of mean age 59.0 ± 9.1 years, of whom 44.8% were women. Mean time to follow-up examination was 53.8 ± 24.5 months. Overall, 376 patients had 5-9 mm HPs proximal to the sigmoid at index examination. Compared with patients with low-risk adenomas, the greatest adjusted risk for metachronous large SPs was observed in patients with large HPs or any SSP or TSA at index examination (OR< 7.63; 95% CI, 4.78-12.20). Of patients with 5-9 mm HPs, risk for metachronous large SPs was also elevated (OR, 4.77; 95% CI, 2.54-8.94). When patients with synchronous adenomas were excluded from analyses, risk for metachronous large SP remained elevated in the 5-9 mm HPs group (OR, 2.92; 95% CI, 1.99-4.29). In initial models, risk for advanced adenomas was increased in patients with 5-9 mm HPs (OR, 1.83; 95% CI, 1.19-2.81) compared with patients with high-risk adenomas. However, when patients with synchronous adenomas were excluded, 5-9 mm proximal HPs no longer predicted increased advanced adenoma risk (OR, 1.50; 95% CI, 0.74-3.04). The number of proximal HPs 5-9 mm at index examination did not appear to influence the risk for metachronous large SPs (P =1.0) or advanced adenomas (P =.46).

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According these data, patients with 5-9 mm HPs proximal to the sigmoid were at greater risk for metachronous large SPs than patients with conventional adenomas and no SPs. This trend persisted after individuals with index SPs who had synchronous adenomas were excluded. These results suggest that patients with proximal 5-9mm HPs may benefit from shorter surveillance intervals than patients with nonsignificant HPs. The researchers note that further study is needed to clarify the optimal follow-up interval for patients in this risk group. Additionally, given the racial and ethnic homogeneity of the population enrolled in the New Hampshire Colonoscopy Registry, results may not be generalizable to the larger population.


Anderson JC, Robinson CM, Butterly LF. Increased risk of metachronous large serrated polyps in individuals with 5 to 9 mm proximal hyperplastic polyps: data from the New Hampshire Colonoscopy Registry [published online April 26, 2020]. Gastrointest Endosc. doi: 10.1016/j.gie.2020.04.034