Characteristics of Large Sessile Serrated Adenoma Resected by Wide Field Endoscopic Mucosal
Resection in a Multicentre Prospective Cohort.
Introduction Serrated lesions (SL) are thought to account for up to 30% of all sporadic colorectal cancers.
Most data is derived from the study of conventional (≤10mm) SL. Larger SL may be at greater risk. The clinical and endoscopic characteristics of large SL are unknown and predictors and risk of invasive neoplasia have not been described. We present data on a large multicentre cohort of patients with SL
≥20mm, in comparison to patients with conventional adenomatous advanced mucosal neoplasia (AMN-C)
Aim To examine the clinical and endoscopic characteristics of SL ≥20mm resected by Wide Field
Endoscopic Mucosal Resection (WF-EMR) in a multicentre prospective cohort and identify risk factors for high grade dysplasia (HGD) or cancer.
Methods Prospective multicenter data of large sessile colorectal polyps or LSTs ≥20 mm referred for resection by wide field endoscopic mucosal resection (EMR) (June 2008-March 2013) was analysed. Data collection included patient and lesion characteristics, procedural outcomes, complications and scheduled follow up at 14 days, 4 and 12 months. Where multiple lesions were resected, one was selected at random for analysis. All SL histology was reviewed by expert gastrointestinal pathologists and classified according to the World Health Organisation criteria (2010).
Results 1361 lesions were analysed in 1254 patients: 193 (14.3%) sessile serrated adenoma (SSA), 16
(1.0%) traditional serrated adenoma (TSA). 1153 (84.7%) were AMN-C (31.7% tubular histology, 63.2% tubulovillous, 3.3% villous, 1.7% other)
Compared to AMN-C, patients with SSA were younger (mean 64.0 vs 68.4 years; p <0.001) and predominantly female (56.4% vs 45.3%; p 0.009). Lesions were smaller (28.4 vs 37.0mm; p <0.001), located proximal to the splenic flexure (88.1% vs 64.6%; p <0.001) and more likely to be Paris type IIa and
Kudo pit pattern II. Cancer diagnosis was lower in SSAs (3.1% vs 9.0% p 0.006)
66 SSAs had cytological dysplasia (SSA-CD) (52 Low Grade Dysplasia (LGD), 8 HGD, 6 cancer). SSA-CD were predominantly Kudo IV and took a greater number of pieces to resect than SSA-ND. Procedural success rates were lower (92.4% vs 99.2%; p 0.020) and recurrence rates higher (4.7% vs 28.6%; p 0.026).
Discrimination of SSA from AMN-C was poorer when SSAs contained dysplasia.
16 TSAs were resected. Patients were predominantly female (87.5% vs 45.3%; p0.001) and had lesions located distal to the splenic flexure (87.5% vs 35.4%; p <0.001) compared to AMN-C. HGD/Cancer rates were similar to AMN-C (12.5% vs 9.0%, p 0.65). TSAs were largely Kudo III (80.0% vs 39.5%, p 0.047).
In SSAs, multiple logistic regression analysis showed HGD/cancer was predicted by Age (OR 2.1 p 0.029, any Paris Is component (OR 12.5 p <0.001) and Kudo pit pattern IV (OR 7.2, p 0.006).
Conclusion Large SSAs are associated with younger age, female sex, smaller lesion size and proximal location compared to AMN-C. Cancer is present in 3.1% and HGD/cancer in 7.3%. SSA-CD are at greater risk of recurrence. SSAs in older patients; with a Paris type Is component; or with Kudo pit pattern IV are more likely to contain cancer or HGD. Large dysplastic SSAs can resemble tubulovillous adenoma.
Morphology is a dominant feature guiding cancer risk in large SSAs and endoscopists should carefully examine these lesions for a Paris Is component