In a retrospective cohort study of 328,416 adult colonoscopies, sessile serrated lesion detection rate (SSLDR) was significantly associated with lower risk for postcolonoscopy colorectal cancer (PCCRC).

The highest quartile of detection of these flat saw-toothed colonic polyps had a statistically significantly lower multivariate hazard ratio of 0.69 (95% CI, 0.50-0.94; P for trend = .01) than the lowest quartile, suggesting that the SSLDR should be a quality metric for colonoscopy along with adenoma detection rate (ADR), according to lead author Edward S. Huang, MD, MPH, a gastroenterologist in the Department of Gastroenterology at Palo Alto Medical Foundation, Sutter Health, in San Jose, California, reporting in JAMA Network Open.

The analysis also found an association between higher SSLDR and lower all-cause and CRC mortality.

“For years, we’ve known that adenoma detection rate is strongly associated with lower colorectal cancer risk,” Huang told Medscape Medical News. “However, sessile serrated lesions represent a distinct and important pathway to CRC — particularly proximal cancers — and yet we lacked strong outcome-based evidence showing that detecting more of these lesions actually translates into fewer cancers.”

The identification of SSLs has lagged behind that of conventional adenomas, Huang added. “SSLs have subtle mucosal features compared with traditional polyps, making them harder to see during colonoscopy and more prone to under-recognition historically.” In addition, pathologic criteria have changed over the time making diagnosis challenging and many were previously misclassified as hyperplastic polyps.

Guidelines have only recently begun recommending SSLDR benchmarks — for example, a minimum of about 6% SSLDR. These recommendations were supported by limited evidence before this study, Huang said. “Uptake of these metrics into routine quality monitoring has been gradual, partly due to diagnostic challenges and evolving nomenclature and pathology criteria for serrated lesions.”

The Study

Conducted from January 2000 to December 2021, the investigators examined colonoscopies by 50 gastroenterologists in 226,695 adult patients with no CRC diagnosis within 6 months of colonoscopy and no history of CRC or inflammatory bowel disease.

The mean age of patients was 58.6 years and 51.7% were women. Among these, 562 PCCRC cases were identified over 2,038,816 person-years of follow-up. The absolute PCCRC incidence rate decreased with higher SSLDR quartiles, from 3.9 cases per 10,000 person-years in the lowest quartile to 2.4 cases per 10,000 person-years in the highest quartile. The association was strongest for proximal colon cancers.

Compared with the lowest SSLDR quartile, the highest SSLDR quartile was also associated with lower all-cause mortality and lower CRC-related mortality.

“Our study provides outcome-based validation that SSLDR is not just a number,” Huang said. “It reflects clinically meaningful cancer prevention.”

Commenting on the study but not involved in it, Douglas K. Rex, MD, a professor emeritus at Indiana University, Indianapolis, and a gastroenterologist in Indianapolis, said that although ADR is now the cornerstone of quality measurement in colonoscopy, “it’s been clear for two decades that adenomas are the precursors of only about 75% of colorectal cancers. The remainder arise from serrated polyps, particularly sessile serrated lesions. There are a group of endoscopists with adequate ADR but low SSLDR, and these endoscopists have higher rates of PCCRC compared to those with high ADR and high SSLDR.”

Rex was first author of recommendations jointly issued in 2024 by the American College of Gastroenterology/American Society for Gastrointestinal Endoscopy that endoscopists measure both their ADR and SSLDR. “The current study provides additional strong support for this recommendation.”

In other comments, Andrew T. Chan, MD, MPH, a gastroenterologist at Massachusetts General Brigham Hospital and a professor of medicine at Harvard Medical School in Boston, agreed that higher SSLDR is a quality metric and a potentially valuable adjunct to ADR.

“These findings are consistent with my clinical experience,” Chan told Medscape Medical News, noting that these often morphologically subtle lesions are easily overlooked. “A higher detection rate likely reflects an endoscopist’s ability to recognize these inconspicuous mucosal changes, suggesting a more meticulous and higher-quality examination.”

As precursors to specific molecular subtypes of colorectal cancer, particularly those arising in the proximal colon, SSLs require complete removal to reduce the risk for PCCRC. “Moreover, a higher SSLDR may reflect broader endoscopic skill, including the ability to identify conventional adenomas that account for most other colorectal cancer subtypes,” Chan added. “SSLDR may serve not only as a serrated pathway-specific metric but also as a more global quality indicator associated with lower risk of PCCRC across molecular subtypes.”

On the practice front, Huang suggested that endoscopists should think beyond adenomas and actively identify and remove SSLs because it affects cancer outcomes. In addition, they should: increase familiarity with the endoscopic appearance of SSLs (flat, mucus-cap, and subtle), use high-resolution scopes and enhanced imaging, review SSLDR as part of endoscopic quality improvement, and collaborate with pathologists to ensure accurate classification of these lesions.

In an accompanying editorial, Joseph C. Anderson, MD, of the Geisel School of Medicine at Dartmouth College in Hanover, New Hampshire, agreed that input from pathology is important. He cautioned that distinguishing SSLs from hyperplastic polyps may increase the endoscopic challenge, and the diagnosis of SSLs may rely on the expertise of pathologists. Endoscopists should discuss the criteria for diagnosing SSLs with their pathologists.

This study was supported by the Palo Alto Medical Foundation. The authors had no conflicts of interest. Rex, Chan, and Anderson had no relevant conflicts of interest.