Prevalence and Clinical Features of Sessile Serrated Polyps: A Systematic Review

Abstract

Background & aims: Sessile serrated polyps (SSPs) could account for a substantial proportion of colorectal cancers. We aimed to increase clarity on SSP prevalence and clinical features.

Methods: We performed a systematic review of MEDLINE, Web of Science, Embase, and Cochrane databases for original studies published in English since 2000. We included studies of different populations (United States general or similar), interventions (colonoscopy, autopsy), comparisons (world regions, alternative polyp definitions, adenoma), outcomes (prevalence, clinical features), and study designs (cross-sectional). Random-effects regression was used for meta-analysis where possible.

Results: We identified 74 relevant colonoscopy studies. SSP prevalence varied by world region, from 2.6% in Asia (95% confidence interval [CI], 0-5.9) to 10.5% in Australia (95% CI, 2.8-18.2). Prevalence values did not differ significantly between the United States and Europe (P = .51); the pooled prevalence was 4.6% (95% CI, 3.4-5.8), and SSPs accounted for 9.4% of polyps with malignant potential (95% CI, 6.6-12.3). The mean prevalence was higher when assessed through high-performance examinations (9.1%; 95% CI, 4.0-14.2; P = .04) and with an alternative definition of clinically relevant serrated polyps (12.3%; 95% CI, 9.3-15.4; P < .001). Increases in prevalence with age were not statistically significant, and prevalence did not differ significantly by sex. Compared with adenomas, a higher proportion of SSPs were solitary (69.0%; 95% CI, 45.9-92.1; P = .08), with diameters of 10 mm or more (19.3%; 95% CI, 12.4-26.2; P = .13) and were proximal (71.5%; 95% CI, 63.5-79.5; P = .008). The mean ages for detection of SSP without dysplasia, with any or low-grade dysplasia, and with high-grade dysplasia were 60.8 years, 65.6 years, and 70.2 years, respectively. The range for proportions of SSPs with dysplasia was 3.7%-42.9% across studies, possibly reflecting different study populations.

Conclusions: In a systematic review, we found that SSPs are relatively uncommon compared with adenoma. More research is needed on appropriate diagnostic criteria, variations in detection, and long-term risk.

Keywords: Colon Cancer; Neoplasm; PICOS; US.

Figure 1.

Prevalence of sessile serrated polyps across included studies. U.S. and European studies. Squares=means; square size=population size; whiskers=95% CIs; polygon=pooled mean, random-effects meta-regression; ***=significant heterogeneity, P<.001.

Figure 2.

Fraction of polyps with sessile serrated histology across included studies. U.S. and European studies. Squares=means; square size=population size; whiskers=95% CIs; polygon=pooled mean, random-effects meta-regression; ***=significant heterogeneity, P<.001. Precancerous lesions include conventional adenoma, SSPs, and traditional serrated adenoma.

Figure 3.

Prevalence of serrated polyps according to clinical definition. U.S and European studies. Whiskers=95% confidence intervals; ***=significant difference vs. SSP prevalence, P<.001. The “clinically relevant” grouping includes definitions combining sessile serrated, traditional serrated polyps and hyperplastic polyps by size (>5 or >10mm) and/or location (proximal). See Suppl.Figure 5 for corresponding Forest plots and more detail on polyp definitions.

Figure 4.

Sessile serrated polyp prevalence according to exam indication and quality level. U.S. and European studies. Whiskers= 95% confidence intervals; *=significant difference vs. prevalence in unselected exams, P<.05. Good–Excellent bowel preparation=by Aronchick scale, 7–9 Boston Bowel Preparation Score, or split-dose; high-quality examinations=enhanced endoscopes or provider from upper quartile of sessile serrated polyp detection. See Suppl.Figure 6 for Forest plots and definitions.

Figure 5.

Prevalence of sessile serrated vs. adenomatous polyps by age. Dots=study observations by age; colors=different U.S. and European studies (Suppl.Table 4–5); size=patient denominator; dashed line=fitted log-linear trends for ages 40–100 years measuring relative increase by age-year; ***=significant trend, P<.001. Some studies in A provided no patient denominator, and were excluded from trends and represented with small constant N.

Figure 6.

Number, size, and localization of sessile serrated vs. adenomatous polyps. U.S. and European studies. See Suppl.Figures 10–12 for Forest plots and Suppl.Tables 7–9 for adenoma data. Whiskers=95% confidence intervals; **=significant differences for SSP vs. adenoma, P<.01 (***P<.001); Size=small (0–5mm), medium (6–9mm), or large (10+mm); location=proximal (cecum, ascending colon, hepatic flexure, transverse colon), distal (splenic flexure, descending colon, sigmoid colon), or rectal.

Figure 7.

Proportion of sessile serrated polyps with cytological dysplasia across studies.* U.S. and European studies, including nonscreening indications. Squares=means; square size=population size; whiskers=95% CIs; polygon=pooled mean, random-effects meta-regression; ***=significant heterogeneity, P<.001.U.S. 7.8% (95%CI, 2.9%–12.6%) vs. European studies 20.6% (95%CI 3.6%–37.5%) (P=.15). For some studies, the relative prevalence of dysplastic vs. all SSPs was used as approximation (Suppl.Table 10). Excluding one outlier, the proportion decreased to 9.7% (95%CI, 4.5%–14.9%; Europe 13.1% (95%CI, 0.6%–25.5%).