P1306 - Increase in Clinically Significant Serrated Polyp Rates Is Due to Higher Detection as Well as Interpretation by Pathologist

Monday, October 25, 2021

10:30 AM – 4:15 PM PT

Location: Shoreline Exhibit Hall

Has Audio

Presenting Author(s)

Joseph Anderson, MD

Physician
White River Junction VA Medical Center
Hanover, New Hampshire, United States

Joseph Anderson, MD¹, William Hisey, MS², Christina Robinson, MS³, Todd Mackenzie, PhD⁴, Lynn Butterly, MD²
¹White River Junction VA Medical Center, Hanover, NH; ²Dartmouth-Hitchcock Medical Center, Hanover, NH; ³Dartmouth-Hitchcock Medical Center, Lebanon, NH; ⁴Dartmouth College Geisel School of Medicine, Hanover, NH

Introduction: Clinically significant serrated polyps (CSSP) may account for a large proportion of CRC. CSSPs are defined as any sessile serrated polyp (SSP), traditional serrated adenoma (TSA), large (>1cm) hyperplastic polyp (HP), or proximal HP 5-9 mm in size. Our aim was to examine the trends in detection of these lesions and the possible impact of pathological interpretation of HP and SSP diagnoses on the changes in observed detection.

Methods: Our sample consisted of 69,540 events in patients 50 years or older enrolled in the NHCR who had a complete screening colonoscopy with adequate bowel preparation. We examined trends in CSSP detection from 2005 to 2019. In order to assess the potential impact of pathological interpretation on CSSP trends, we created a counterfactual CSSP definition including any TSAs, but only HPs/SSPs >1cm or proximal 5-9mm HPs/SSPs, thereby treating SSPs like HPs and eliminating the importance of pathological diagnosis. In other words, we included only those SSPs that would be counted as CSSPs even if they were HPs. We looked at changes over time in the relative prevalence of proximal SSPs < 5mm and distal SSPs < 10mm – SSPs excluded by the alternative CSSP criteria. Finally, simple logistic regression models were used to examine trends over time.

Results: Our sample included data from 69,540 exams (average age 59.3, 44.9% male). Figure 1 shows detection rates for three types of lesions from 2005-2019: CSSPs, with a 12% per year increase from 4.4% to 12.8% (OR=1.12 95% CI 1.11-1.13), counterfactual CSSPs, with a 9% per year increase from 4.3% to 9.4% (OR=1.09 95% CI 1.07-1.10), and SSPs excluded from the counterfactual CSSP definition, with a 28% per year increase from 0.0% to 3.7% (OR=1.28 95% CI 1.25-1.31). Finally, the proportion of proximal HPs/SSPs < 5mm diagnosed as SSPs increased from 0.0% to 36.5% or by 28% per year (OR=1.28 95% 1.24-1.32) (Figure 2), compared to a more modest 14% increase for distal HPs/SSPs < 10mm diagnosed as SSPs from 1.3% to 6.8% (OR=1.14 95% 1.10-1.18).

Discussion: There was a significant increase in the CSSP detection rate in the NHCR from 2005-2019, even after accounting for a sustained rise in the proportion of events with SSPs relative to those with HPs. However, the difference between the overall and counterfactual CSSP detection rate trends suggests that increased interpretation of serrated polyps as SSPs may explain a large part of the increase in CSSP detection.

Figure: On the three-line graph, blue is the CSSP detection rate, red is the CSSP with SSPs treated like HPs detection rate, and green is the detection rate for SSPs that would not count as CSSPs if the HP criteria were applied (proximal SSPs <5mm and distal SSPs <10mm). On the single-line graph, gray is events with proximal SSPs <5mm as a proportion of all events with proximal HPs/SSPs <5mm.

Table 1 Absolute and Adjusted Trends in Serrated Polyp Detection

Trend	Absolute 2005-19	OR	95% CI
CSSP	4.4% to 12.8%	1.12	1.11-1.13
Counterfactual CSSP	4.3% to 9.4%	1.09	1.07-1.10
SSPs not included as counterfactual	0.0% to 3.7%	1.28	1.25-1.31
Proportion of proximal HPs/SSPs < 5 mm diagnosed as SSPs	0.0% to 36.5%	1.28	1.24-1.32
Proportion of distal HPs/SSPs < 10 mm diagnosed as SSPs	1.3% to 6.8%	1.14	1.10-1.18

Disclosures:

Joseph Anderson indicated no relevant financial relationships.

William Hisey indicated no relevant financial relationships.

Christina Robinson indicated no relevant financial relationships.

Todd Mackenzie indicated no relevant financial relationships.

Lynn Butterly indicated no relevant financial relationships.

Joseph Anderson, MD¹, William Hisey, MS², Christina Robinson, MS³, Todd Mackenzie, PhD⁴, Lynn Butterly, MD². P1306 - Increase in Clinically Significant Serrated Polyp Rates Is Due to Higher Detection as Well as Interpretation by Pathologist, ACG 2021 Annual Scientific Meeting Abstracts. Las Vegas, Nevada: American College of Gastroenterology.