Endoscopic Surveillance Research Articles

Cancer Progress and Priorities: Gastric Cancer.

Gastric cancer, the fifth leading cause of cancer worldwide, is estimated to be responsible for approximately 1.4% of all new cancers and 1.8% of all cancer-related deaths in the United States. Despite declining incidence rates and improved survival rates, however, gastric cancer continues to disproportionately affect racial and ethnic minorities and individuals of lower socioeconomic status at higher rates than the general population. To improve outcomes globally and address disparities within the United States, continued improvements are needed in risk factor modification and biomarker development and to improve access to existing preventative measures such as genetic testing and H. pylori eradication testing, in addition to expanding upon current clinical guidelines for premalignant disease to address gaps in endoscopic surveillance and early detection.

Personalized endoscopic surveillance and intervention protocols for patients with familial adenomatous polyposis: the European FAP Consortium strategy.

Background and study aims Patients with familial adenomatous polyposis (FAP) undergo colectomy and lifelong endoscopic surveillance to prevent colorectal, duodenal and gastric cancer. Endoscopy has advanced significantly in recent years, including both detection technology as well as treatment options. For the lower gastrointestinal tract, current guidelines do not provide clear recommendations for surveillance intervals. Furthermore, the Spigelman staging system for duodenal polyposis has its limitations. We present a newly developed personalized endoscopic surveillance strategy for the lower and upper gastrointestinal tract, aiming to improve the care for patients with FAP. We aim to inform centers caring for FAP patients and encourage the discussion on optimizing endoscopic surveillance and treatment in this high-risk population. Methods The European FAP Consortium, consisting of endoscopists with expertise in FAP, collaboratively developed new surveillance protocols. The proposed strategy was consensus-based and a result of several consortium meetings, discussing current evidence and limitations of existing systems. This strategy provides clear indications for endoscopic polypectomy in the rectum, pouch, duodenum and stomach and defines new criteria for surveillance intervals. This strategy will be evaluated in a 5-year prospective study in nine FAP expert centers in Europe. Results We present a newly developed personalized endoscopic surveillance and endoscopic treatment strategy for patients with FAP aiming to prevent cancer, optimize endoscopic resources and limit the number of surgical interventions. Following this new strategy, prospectively collected data in a large cohort of patients will inform us on the efficacy and safety of the proposed approaches.

Cancer surveillance as an alternative to prophylactic total gastrectomy in hereditary diffuse gastric cancer: a prospective cohort study.

Loss of function variants in CDH1 are the most frequent cause of hereditary diffuse gastric cancer. Endoscopy is regarded as insufficient for early detection due to the infiltrative phenotype of diffuse-type cancers. Microscopic foci of invasive signet ring cells are pathognomonic of CDH1 and precede development of diffuse gastric cancer. We aimed to assess the safety and effectiveness of endoscopy for cancer interception in individuals with germline CDH1 variants, particularly in those who declined prophylactic total gastrectomy. In this prospective cohort study, we included asymptomatic patients aged 2 years or older with pathogenic or likely pathogenic germline CDH1 variants who underwent endoscopic screening and surveillance at the National Institutes of Health (Bethesda, MD, USA) as part of a natural history study of hereditary gastric cancers (NCT03030404). Endoscopy was done with non-targeted biopsies and one or more targeted biopsy and assessment of focal lesions. Endoscopy findings, pathological data, personal and family cancer history, and demographics were recorded. Procedural morbidity, gastric cancer detection by endoscopy and gastrectomy, and cancer-specific events were assessed. Screening was defined as the initial endoscopy and all subsequent endoscopies were considered surveillance; follow-up endoscopy was at 6 to 12 months. The primary aim was to determine effectiveness of endoscopic surveillance for detection of gastric signet ring cell carcinoma. Between Jan 25, 2017, and Dec 12, 2021, 270 patients (median age 46·6 years [IQR 36·5-59·8], 173 [64%] female participants, 97 [36%] male participants; 250 [93%] were non-Hispanic White, eight [3%] were multiracial, four [2%] were non-Hispanic Black, three [1%] were Hispanic, two [1%] were Asian, and one [<1%] was American Indian or Alaskan Native) with germline CDH1 variants were screened, in whom 467 endoscopies were done as of data cutoff (April 30, 2022). 213 (79%) of 270 patients had a family history of gastric cancer, and 176 (65%) reported a family history of breast cancer. Median follow-up was 31·1 months (IQR 17·1-42·1). 38 803 total gastric biopsy samples were obtained, of which 1163 (3%) were positive for invasive signet ring cell carcinoma. Signet ring cell carcinoma was detected in 76 (63%) of 120 patients who had two or more surveillance endoscopies, of whom 74 had occult cancer detected; the remaining two individuals developed focal ulcerations each corresponding to pT3N0 stage carcinoma. 98 (36%) of 270 patients proceeded to prophylactic total gastrectomy. Among patients who had a prophylactic total gastrectomy after an endoscopy with biopsy samples negative for cancer (42 [43%] of 98), multifocal stage IA gastric carcinoma was detected in 39 (93%). Two (1%) participants died during follow-up, one due to metastatic lobular breast cancer and the other due to underlying cerebrovascular disease, and no participants were diagnosed with advanced stage (III or IV) cancer during follow-up. In our cohort, endoscopic cancer surveillance was an acceptable alternative to surgery in individuals with CDH1 variants who declined total gastrectomy. The low rate of incident tumours (>T1a) suggests that surveillance might be a rational alternative to surgery in individuals with CDH1 variants. Intramural Research Program, National Institutes of Health.

Surveillance in Barrett’s Esophagus: Challenges, Progress, and Possibilities

Endoscopic surveillance of Barrett's esophagus, aiming to detect prevalent dysplasia and adenocarcinoma, followed by effective endoscopic treatment, is an integral part of the esophageal adenocarcinoma prevention paradigm. However, several limitations, such as the subtle appearance of dysplasia, sampling error (inherent in current surveillance protocols), and noncompliance with surveillance recommendations, lead to missed dysplasia and neoplasia, reducing the effectiveness of surveillance as currently practiced. Careful endoscopic assessment with high-resolution white-light endoscopy, dye-based or electronic chromoendoscopy, and comprehensive sampling of the BE mucosa, remains the cornerstone of endoscopic surveillance. Emerging innovations in this area span the gamut of more efficient sampling methods, advanced imaging tools, artificial intelligence, and molecular marker-powered approaches as adjuncts, to identify prevalent and predict incident dysplasia or adenocarcinoma. Development and implementation of validated quality indicators will allow additional advancement of this critical field. These approaches will hopefully enable efficient and effective cancer prevention and treatment.

Endoscopic surveillance: time for a paradigm shift in hereditary diffuse-type gastric cancer management?

Endoscopic surveillance: time for a paradigm shift in hereditary diffuse-type gastric cancer management?

Obesity, sleeve gastrectomy and gastro-esophageal reflux disease.

Sleeve gastrectomy (SG) is the most frequently performed operation for morbid obesity in the world. In spite of its demonstrated efficacy, the Achilles' Heel of this procedure seems to be either pre-existing or de novo gastro-esophageal reflux disease (GERD) with its potential complications such as peptic esophagitis, Barrett's esophagus and, in the long-term, esophageal adenocarcinoma. According to factual literature, it appears clear that Roux-en-Y gastric bypass is the preferred choice in case of pre-existing GERD or hiatal hernia discovered during preoperative workup for bariatric surgery. Nonetheless, certain authors propose performance of SG with an associated antireflux procedure such as Nissen fundoplication. Strict endoscopic surveillance is recommended after bariatric surgery. Revisional surgery (conversion of SG into Roux-en-Y gastric bypass (RYGB)) is the treatment of choice for patients who develop GERD after SG when conservative treatment (modified lifestyle and proton pump inhibitors) has failed. Lastly, with regard to the risk of esophageal adenocarcinoma after SG, large scale studies with adequate follow-up are necessary to come to factual conclusions. In all cases, the management of this conundrum remains a major technical challenge that has to be taken in consideration in future years, especially because of the current expansion of bariatric surgery.

Hereditary Diffuse Gastric Cancer

Hereditary diffuse gastric cancer (HDGC) is a dominantly inherited cancer syndrome characterized by a high incidence of diffuse gastric cancer (DGC) and lobular breast cancer (LBC). HDGC is caused by germline mutations in 2 genes involved in the epithelial adherens junction complex, CDH1 and CTNNA1. We discuss the genetics of HDGC and the variability of its clinical phenotype, in particular the variable penetrance of advanced DGC and LBC, both within and between families. We review the pathology of the disease, the mechanism of tumor initiation, and its natural history. Finally, we describe current best practice for the clinical management of HDGC, including emerging genetic testing criteria for the identification of new families, methods for endoscopic surveillance, the complications associated with prophylactic surgery, postoperative quality of life, and the emerging field of HDGC chemoprevention.

Clinical characteristics and long-term prognosis of type 1 gastric neuroendocrine tumors in a large Japanese national cohort.

Optimal management of type 1 gastric neuroendocrine tumors (T1-GNETs) remains unknown, with few reports on their long-term prognosis. This study investigated the clinical characteristics and long-term prognosis of T1-GNETs. We reviewed the medical records of patients diagnosed with T1-GNET during 1991-2019 at 40 institutions in Japan. Among 172 patients, endoscopic resection (ER), endoscopic surveillance, and surgery were performed in 84, 61, and 27, respectively, including 27, 77, and 2 patients with pT1a-M, pT1b-SM, and pT2 tumors, respectively. The median tumor diameter was 5 (range 0.8-55) mm. Four (2.9%) patients had lymph node metastasis (LNM); none had liver metastasis. LNM rates were significantly higher in tumors with lymphovascular invasion (LVI) (15.8%; 3/19) than in those without (1.1%; 1/92) (P=0.016). For tumors <10 mm, LVI and LNM rates were 18.4% (14/76) and 2.2% (2/90), respectively, which were not significantly different from those of tumors 10-20 mm (LVI 13.3%; 2/15, P=0.211; and LNM 0%; 0/17, P=1.0). However, these rates were significantly lower than those of tumors >20 mm (LVI 60%; 3/5, P=0.021; and LNM 40%; 2/5, P=0.039). No tumor recurrence or cause-specific death occurred during the median follow-up of 10.1 (1-25) years. The 10-year overall survival rate was 97%. Type 1 gastric neuroendocrine tumors showed indolent nature and favorable long-term prognoses. LVI could be useful in indicating the need for additional treatments. ER for risk prediction of LNM should be considered for tumors <10 mm and may be feasible for tumors 10-20 mm. The study protocol was registered in the University Hospital Medical Information Network (UMIN) under the identifier UMIN000029927.

Long-term endoscopic surveillance in HBV compensated cirrhotic patients treated with Tenofovir or Entecavir for 11 years.

Long-term administration of TDF/ETV in patients with HBV-related compensated cirrhosis reduces HCC and decompensation events but the effect of this regimen on development/regression of oesophageal varices (EV) is currently unknown. To assess the risk of EV development/progression in this population. A total of 186 Caucasian HBV-monoinfected compensated cirrhotics were enrolled in a long-term cohort study from TDF/ETV introduction. Upper GI endoscopies were performed according to Baveno recommendations. Primary endpoint was development/progression of oesophageal/gastric varices over time. At TDF/ETV start, median age was 61 years, 80% males, 60% HBV-DNA undetectable, 63% NUCs previously exposed, 73% normal ALT, 40% platelets <150,000/mmc and 25 (13%) with low-risk varices (LRV). During 11 years of antiviral therapy and 666 endoscopies performed, 9 patients either developed or had a progression of oesophageal or gastric varices with an 11-year cumulative probability of 5.1% (95% CI 3-10%); no patient bled. Out of 161 patients without EV at baseline, the 11-year probably was 4.5% with all varices developing within the first six years of treatment. In 25 patients with LRV at baseline, the 11-year probability of progression or regression was 9.3% and 58%, respectively. Only baseline platelet count (HR 0.96, p=0.028) was associated with LRV development at multivariate analysis: platelet ≤90,000/mmc (AUROC 0.70) had 98.1% specificity, 42.9% sensitivity, 50% PPV for LRV onset. In compensated cirrhotic patients under long-term effective TDF/ETV treatment, the 11-year risk of developing/progressing EV is negligible, thus challenging the current endoscopic surveillance recommendations in patients without EV at baseline.

Seattle Protocol Is More Effective in Detection of Dysplasia Compared to Technology-Assisted Targeted Biopsies in Patients with Barrett's Esophagus.

With the development of narrow-band imaging (NBI) in the endoscopic evaluation of patients with Barrett's esophagus (BE), the role of random biopsies according to the Seattle protocol (SP) has been questioned. We aim to compare the utility of advanced imaging to SP in patients with BE. A prospective cohort of patients with proven BE was retrospectively analyzed. All biopsies were reviewed by an expert GI pathologist. Advanced imaging was tandemly used with SP in each endoscopic procedure. A total of 155 out of 340 patients (45.5%) with BE were diagnosed with dysplasia during a median follow-up of 4.7 years (IQR 3.4-6.1 years) and were part of the statistical analysis. A total of 82 patients had a diagnosis of dysplasia at presentation, whereas 84 patients developed dysplasia during follow up. A total of 67 out of 82 patients with dysplasia at presentation (81.7%), and 65 out of 84 patients that were diagnosed with dysplasia during follow-up (77.4%) were diagnosed using SP. In addition, whereas all the events of EAC were diagnosed using targeted biopsies, 57.1% of the events of HGD and 86.3% of LGD were diagnosed using SP. Our findings demonstrate the significance of SP in the detection of low- and high-grade dysplasia in patients with BE. SP should remain the mainstay of endoscopic surveillance in this population.

Management of Barrett’s Esophagus: Practice-Oriented Answers to Clinical Questions

Barrett's esophagus is the most important complication of gastro-esophageal reflux disease and the only known precursor of esophageal adenocarcinoma. The diagnosis and treatment of Barrett's esophagus are clinically challenging as it requires a high level of knowledge and competence in upper gastrointestinal endoscopy. For instance, endoscopists should know when and how to perform biopsies when Barrett's esophagus is suspected. Furthermore, the correct identification and treatment of dysplastic Barrett's esophagus is crucial to prevent progression to cancer as well as it is the endoscopic surveillance of treated patients. Herein, we report practice-oriented answers to clinical questions that clinicians should be aware of when approaching patients with Barrett's esophagus.

Interleukin-10 Knockout Mice Do Not Reliably Exhibit Macroscopic Inflammation: A Natural History Endoscopic Surveillance Study.

Interleukin (IL)-10 knockout (KO) mice, a model for inflammatory bowel disease (IBD), develop chronic enterocolitis due to an aberrant immune response to enteric antigens. Endoscopy, the gold standard for evaluation of human mucosal health, is not widely available for murine models. To assess the natural history of left-sided colitis in IL-10 KO mice via serial endoscopies. BALB/cJ IL-10 KO mice underwent regular endoscopic assessments from 2 up to 8months of age. Procedures were recorded and blindly evaluated using a 4-component endoscopic score: mucosal wall transparency, intestinal bleeding, focal lesions and perianal lesions (0-3 points each). An endoscopic score ≥ 1 point was considered as the presence of colitis/flare. IL-10 KO mice (N = 40, 9 female) were assessed. Mean age at first endoscopy was 62.5 ± 2.5days; average number of procedures per mouse was 6.0 ± 1.3. A total of 238 endoscopies were conducted every 24.8 ± 8.3days, corresponding to 124.1 ± 45.2days of surveillance per mouse. Thirty-three endoscopies in 24 mice (60%) detected colitis, mean endoscopy score 2.5 ± 1.3 (range: 1-6.3). Nineteen mice (47.5%) had one episode of colitis and 5 (12.5%) had 2-3 episodes. All exhibited complete spontaneous healing on subsequent endoscopies. In this large-scale endoscopic surveillance study of IL-10 KO mice, 40% of mice did not develop endoscopic left-sided colitis. Furthermore, IL-10 KO mice did not exhibit persistent colitis and universally exhibited complete spontaneous healing without treatment. The natural history of colitis in IL-10 KO mice may not be comparable with that of IBD in humans and requires careful consideration.

What Is the Risk? Epidemiology and Evidence for Surveillance Regimens.

Patients with inflammatory bowel disease (IBD) have increased risk of colorectal cancer (CRC). The risk for CRC is positively correlated to the duration of disease, extent of colonic involvement, and severity of inflammation. After 8 to 10 years of IBD diagnosis, the risk for CRC rises substantially and screening colonoscopy is recommended. Surveillance colonoscopy interval ranges from 1 to 5 years depending on patient and disease-specific risk factors. IBD patients with high risk factors such as having concomitant primary sclerosing cholangitis, moderate-to-severe inflammation, first-degree relative with CRC at early age, or history of invisible dysplasia or high-risk visible dysplasia should undergo surveillance colonoscopy in 1 year. Meanwhile, those with minimal colonic involvement or ≥2 consecutive unremarkable examinations while in continuous remission may consider extending the surveillance interval to 5 years. Advance in colonoscopy technique such as chromoendoscopy using dyes and/or image digital processing (virtual chromoendoscopy) may enhance dysplasia detection and is the preferred method for IBD surveillance. In the era of high-definition colonoscope, the practice of obtaining extensive biopsies throughout the colon remains controversial but is generally recommended to improve the detection rate of invisible dysplasia. Endoscopic surveillance in IBD has been shown to result in earlier detection of CRC and improved prognosis.

A155 OUTCOMES FOLLOWING ENDOSCOPIC RESECTION OF DUODENAL NEUROENDOCRINE TUMOURS FROM A TERTIARY-CARE ACADEMIC CENTRE

Abstract Background Duodenal neuroendocrine tumours (D-NET) are rare cancers derived from neuroendocrine cells of the duodenum. A steady increase in the incidence of these tumours has been observed. Current treatment and surveillance strategies are guided by various tumour characteristics including size, grade, and depth of invasion. There exists conflicting evidence, however, on the rates of recurrence after positive resection margins following endoscopic resection. Thus, it remains uncertain whether complete endoscopic resection (R0) of these indolent tumours is clinically significant and whether follow-up endoscopic or surgical intervention is justified. Purpose Our aim is to characterize endoscopic management and clinical outcomes in patients undergoing endoscopic resection of D-NETs. Method We conducted a retrospective, single-centre cohort study at The Centre for Advanced Therapeutic Endoscopy and Endoscopic Oncology at St. Michael’s Hospital, Toronto, Ontario. Consecutive patients over the age of 18 who underwent endoscopic resection of histologically proven D-NETs between 2011 and 2020 were included. Data on patient, endoscopic, and tumour characteristics were collected through electronic chart review. Descriptive statistics were conducted for data analysis. Result(s) A total of 155 foregut neuroendocrine tumours (NET) were endoscopically resected amongst 96 patients during the study period. 47 of these were histologically identified as D-NETs. Mean tumour size was 9.88 ± 6.86 mm. Conventional endoscopic mucosal resection (EMR) was performed most frequently (55%, n=26/47), followed by cap-assisted EMR (30%, n=14/47). Hybrid endoscopic submucosal dissection (ESD)/EMR was performed in one case. A total of two intra-procedural perforations occurred, both of which were successfully closed endoscopically. One patient with a peri-ampullary D-NET experienced significant intra-procedural bleeding requiring Hemospray® and subsequent endotracheal intubation resulting in a brief hospitalization. 57% of all resected D-NETs were followed at surveillance endoscopy 1 (SE1) at a median interval of 199 days (range, 84 to 830). Positive resection margins (R1) were found in 26 cases (55%), of which 16 were assessed at SE1 while nine were lost to follow-up. One patient with R1 margins was electively treated with APC at SE1. Tumour recurrence at SE1 occurred in only two patients. Image Conclusion(s) D-NET recurrence is found in less than 5% of patients at surveillance endoscopy following endoscopic resection in spite of a high R1 resection rate. Given this indolent nature of these tumours, our study suggests that patients with positive resection margins can be followed conservatively with surveillance endoscopy. Further investigation is warranted to determine the optimal duration and surveillance strategy for these patients. Please acknowledge all funding agencies by checking the applicable boxes below CAG Disclosure of Interest None Declared

A156 OUTCOMES FOLLOWING ENDOSCOPIC RESECTION OF GASTRIC NEUROENDOCRINE TUMOURS FROM A TERTIARY-CARE ACADEMIC CENTRE

Abstract Background Gastric neuroendocrine tumours (G-NET) are rare cancers derived from neuroendocrine cells of the stomach. A steady increase in the incidence of these tumours has been observed. Current treatment and surveillance strategies are guided by various tumour characteristics including size, grade, and depth of invasion. There exists conflicting evidence, however, on the rates of recurrence from positive resection margins following primary endoscopic resection. Thus, it remains uncertain whether complete endoscopic resection (R0) of these indolent tumours is clinically significant and whether follow-up endoscopic or surgical intervention is justified. Purpose Our aim is to characterize current management patterns and clinical outcomes in patients undergoing endoscopic resection of G-NETs. Method We conducted a retrospective, single-centre cohort study at The Centre for Advanced Therapeutic Endoscopy and Endoscopic Oncology at St. Michael’s Hospital, Toronto, Ontario. Consecutive patients over the age of 18 who underwent endoscopic resection of histologically proven G-NETs between 2011 and 2020 were included. Data on patient, endoscopic, and tumour characteristics were collected through electronic chart review. Descriptive statistics were conducted for data analysis. Result(s) A total of 155 foregut neuroendocrine tumours were endoscopically resected during the study period, of which 108 were identified as G-NETs. 95.3% were classified as Type I. Mean tumour size was 8.93 ± 5.27 mm. Cap-assisted EMR was performed most frequently (n=51), followed by conventional EMR (n=35). ESD was performed in eight cases. Seven intra-procedural perforations occurred, of which all were closed endoscopically. One patient experienced post-procedural perforation requiring ICU and surgery. Positive resection margins (R1) were found in 25% of cases (n=27), of which 78% were assessed at surveillance endoscopy 1 (SE1). Six patients with R1 margins were referred for surgical evaluation and four were lost to follow-up. 78% of all resected G-NETs were followed at SE1 with a median interval of 196 days (range, 23 to 3373). SE1 recurrence rate at the primary resection site was 14% (n=12), of which two were from routine scar biopsies in the absence of endoscopically identifiable recurrence. All visible recurrences at these sites (n=10) were managed with repeat endoscopic resection. Patient and tumour characteristics in the evaluation of G-NET recurrence are presented in Table I. Image Conclusion(s) G-NET recurrence occurs in less than 15% of patients at surveillance endoscopy following endoscopic resection in spite of a predictably higher R1 resection rate. Patient, endoscopic, and tumour factors including method of resection and margin status do not appear to impact the development of early recurrence. Given the indolent nature of these tumours, patients with positive resection margins can be followed conservatively. Further investigation is warranted to determine the optimal duration and surveillance strategy for these patients. Please acknowledge all funding agencies by checking the applicable boxes below None Disclosure of Interest None Declared

A131 ENDOSCOPIC SUBMUCOSAL DISSECTION OF COLORECTAL ADENOMAS AND EARLY ADENOCARCINOMAS: OUTCOMES FROM BRITISH COLUMBIA

Abstract Background Endoscopic resection is the standard of care for the management of colorectal polyps. Larger and more complex polyps require endoscopic mucosal resection (EMR). While complications have been low, EMR is often piecemeal, resulting in indeterminant margins and often a higher recurrence rate. Endoscopic submucosal dissection (ESD) is an advanced endoscopic resection technique with a higher rate of en bloc resection. While more data exist for the resection of gastric lesions with ESD, ESD is becoming more widely used in western countries for the resection of colorectal lesions. Purpose The purpose of this study is to report on the outcomes and rates of complications for colorectal ESD completed in a tertiary centre in British Columbia. Method All colorectal ESD was completed by a senior therapeutic endoscopist who has previously received training in Japan. Retrospective data were collected on all colorectal ESD procedures done in St. Paul’s Hospital from July 11th, 2016, when the procedure first became available, to Aug 30th, 2022. Inclusion criteria were all adults who have undergone ESD for resection of a colorectal lesion. Exclusion criteria were patients younger than 18. Data collected included demographic variables, polyp characteristics, procedural outcomes, and complications. Result(s) A total of 39 ESD procedures were completed. The mean size of the resected lesion was 30.4 mm (range: 5 – 60 mm). Technical success, defined as successful resection of all polypoid tissue, was achieved in 35/39 procedures (89.7%). En-bloc resection was achieved in 27/35 (77.1%) of the completed ESD. The rate of R0 resection was 22/35 (62.9%). Curative resection, defined as technically successful ESD with R0 margin and no lymphovascular invasion, was achieved in 23/39 (59.0%) of the cases and the majority of the patients with non-curative resection that underwent endoscopic surveillance had no recurrence on follow-up. In our cohort, 3/39 (7.7%) patients had adenocarcinoma. None of the ESD resulted in any intra-procedural or delayed perforation. 3/39 (7.7%) patients had clinically significant post-endoscopic resection bleeding. Out of 24 patients that completed follow-up, 4 (16.7%) had recurrence at the resection site that was managed endoscopically. 4/39 (10.3%) of patients required surgery post-ESD. Conclusion(s) In our cohort, ESD is an effective endoscopic resection modality for the management of colorectal adenomas and early adenocarcinoma with a high rate of technical success and low rates of complications. Although the rate of curative resection was low, most were the result of R1 or Rx resection and a majority of the follow-ups in this subgroup demonstrated no further recurrence. The rate of en bloc resection is high, especially given the average size of adenomas in this cohort. Although ESD requires high technical proficiency, its favorable outcomes and low complication rates make ESD highly feasible for the resection of colorectal lesions. Please acknowledge all funding agencies by checking the applicable boxes below None Disclosure of Interest None Declared

A138 SERRATED POLYPOSIS SYNDROME IN INFLAMMATORY BOWEL DISEASE: A SEQUELAE OF CHRONIC DISEASE ACTIVITY OR NEW WHO PHENOTYPE?

Abstract Background Serrated polyposis syndrome (SPS) is a growing health concern with up to 1 in 125 universal screening program participants meeting diagnostic criteria. Conversely, SPS in inflammatory bowel disease (IBD) is rarely described in the literature, despite the predisposition for serrated epithelial change and serrated polyps in this population. Purpose To describe a case of World Health Organization (WHO) criterion I SPS in a patient with IBD, and discuss the existing literature on this rare occurrence. Method Case report and review of the literature. Result(s) Case Report A 53-year-old female with ulcerative colitis (UC; Phenotype: Left-sided; Duration of disease: 40 years; Medical therapy: sulfasalazine) undergoing regular endoscopic surveillance was recently found to have multiple serrated-class lesions including 6 in the sigmoid colon ranging between 8-30mm in size; this included 3 sessile serrated lesions (SSLs) between 20-30mm removed by piecemeal cold snare resection without complication and 2 residual large SSLs for staged endoscopic resection. No endoscopic disease activity was appreciated (Mayo 0), with histopathology of the sigmoid colon and rectum demonstrating chronic inactive colitis. Literature Review From 2008 to 2021, there are eleven reported cases of SPS in IBD. Six patients had UC and most were in remission for several decades at the time of SPS diagnosis. Most SPS cases met WHO criteria and fit within described phenotypes. While the case above meets WHO criterion I for SPS, the presence of large distal lesions is atypical, raising the question of whether chronic disease activity contributed to the development of these serrated lesions, given the known predisposition for serrated epithelial change and serrated lesions in patients with colonic IBD. Image Conclusion(s) SPS in patients with IBD is rare. Questions remain about the role of chronic disease activity contributing to the formation of serrated lesions, its clinical relevance, and optimal management strategy. Please acknowledge all funding agencies by checking the applicable boxes below None Disclosure of Interest None Declared

A228 SAFETY AND EFFICACY OF ENDOSCOPIC RESECTION OF NON-AMPULLARY DUODENAL POLYPS AND RISK OF POLYP RECURRENCE

Abstract Background Non-ampullary duodenal adenomas, which can present sporadically or in the context of a polyposis syndrome, carry a risk of progression to carcinoma in a similar sequence to colorectal adenomas. Complete endoscopic resection is recommended as first line as a less invasive alternative to surgical rsection. Identifying recurrence rates of non-ampullary duodenal polyps after endoscopic resection, and patient and polyp characteristics associated with recurrence is important in determining the best method of resection and guiding endoscopic surveillance. Purpose To determine the technical success rate of endoscopic resection of non-ampullary duodenal polyps, complication rates, rate of residual and recurrent polyps, and identify factors associated with polyp recurrence. Method All adult patients (≥18 years) that underwent endoscopic resection of non-ampullary duodenal polyps at St. Michael’s Hospital, a Canadian tertiary referral center, from January 2010 to June 2021 were retrospectively identified. Descriptive statistics were calculated for variables of interest and Chi-square, t-test or U-Mann Whitney tests were used to compare variables as appropriate. Bi-variate regression analysis was utilized to determine co-variables associated with recurrence. Result(s) A total of 300 patients underwent endoscopic resection of duodenal polyps. Table 1 describes patient demographics, polyp and procedural characteristics and characteristics associated with recurrence. Nearly all cases were technically successful (96%, n=286/299). Clinically significant intraprocedural bleeding occurred in 22% (n=65/300) of patients, and deep mural injury occurred in 3% (n=7/284) of patients. Delayed post-procedural bleeding occurred in 9% of patients (n=26/279). The median time to first surveillance EGD was 4 months. Polyp recurrence occurred in 28% (n=50/180) of patients. Of the patients with polyp recurrence, 82% (n=42/50) were successfully managed endoscopically. On univariate analysis, polyp size (OR 1.03, 95% CI 1.01-1.06), piecemeal resection (OR 1.63, 95% CI 0.17-0.82), intraprocedural bleeding (OR 2.28, 95% CI 1.09-4.74), and high-grade dysplasia (HGD) or intramucosal adenocarcinoma (IMCa) on final histology (OR 3.46, 95% CI 1.64-7.33) were significantly associated with polyp recurrence. On multivariate analysis, only HGD/IMCa on final histology was significant (OR 3.41, 95% CI 1.38-8.47). Image Conclusion(s) Endoscopic resection of duodenal polyps can be safely performed with high technical success, however recurrence is a significant concern. Advanced histology was a significant predictor of polyp recurrence and highlights the importance of accurate pre-resection endoscopic characterization to correctly identify lesions at increased risk that may benefit from alternative resection methods such as ESD or hot rather than cold EMR, and which may require closer follow-up. Future work to develop predictive models of recurrence are needed to better stratify patient risk. Please acknowledge all funding agencies by checking the applicable boxes below None Disclosure of Interest None Declared

Local Recurrence after Endoscopic Submucosal Dissection of Early Gastric Cancer

Endoscopic submucosal dissection (ESD) is considered the treatment of choice for early gastric cancer (EGC) with a negligible risk of lymph node metastasis. Locally recurrent lesions on artificial ulcer scars are difficult to manage. Predicting the risk of local recurrence after ESD is important to manage and prevent the event. We aimed to elucidate the risk factors associated with local recurrence after ESD of EGC. Between November 2008 and February 2016, consecutive patients (n = 641; mean age, 69.3 ± 9.5 years; men, 77.2%) with EGC who underwent ESD at a single tertiary referral hospital were retrospectively analyzed to evaluate the incidence and factors associated with local recurrence. Local recurrence was defined as the development of neoplastic lesions at or adjacent to the site of the post-ESD scar. En bloc and complete resection rates were 97.8% and 93.6%, respectively. The local recurrence rate after ESD was 3.1%. The mean follow-up period after ESD was 50.7 ± 32.5 months. One case of gastric cancer-related death (0.15%) was noted, wherein the patient had refused additive surgical resection after ESD for EGC with lymphatic and deep submucosal invasion. Lesion size ≥15 mm, incomplete histologic resection, undifferentiated adenocarcinoma, scar, and the absence of erythema of the surface were associated with a higher risk of local recurrence. Predicting local recurrence during regular endoscopic surveillance after ESD is important, especially in patients with a larger lesion size (≥15 mm), incomplete histologic resection, surface changes of scars, and no erythema of the surface.

Role of ablative therapy for squamous cell neoplasia of esophagus

: Esophageal squamous cell neoplasia (ESCN) is the histologic precursor to esophageal squamous cell carcinoma (ESCC), which causes a large burden of disease across the world. Over the past years, on account of the rapid development of endoscopic techniques with highly effectiveness and less invasiveness, the management of ESCN had changed from radical esophagectomy towards endoscopic therapeutics, including endoscopic resection (ER) and ablation techniques. Compared with ER, ablative techniques offer more convenient and safe modality, showing a reasonable efficacy and promising results in eradicating ESCN. Two most widely used ablative therapies for ESCN are radiofrequency ablation and cryoablation. Radiofrequency ablation ablates tissue through heat, while cryoablation coagulates tissue through cold. Recent data show that radiofrequency ablation is highly effective and durable in the removal of early ESCN, and demonstrates a lower rate of stenosis in treating large and extensive ESCN. Meanwhile, cryoablation also demonstrates relatively satisfactory short-term outcome in eradicating ESCN. However, there is still a risk of recurrence and residual lesions for both RFA and cryoablation when treating ESCN. Considering that complete tissue destruction of ablation does not allow histological assessment, staging the neoplasia and deciding which patient may be an ablation candidate before treatment is of great importance, and endoscopic surveillance with Lugol’s chromoendoscopy is also necessary to detect any recurrence and metachronous lesions. Moreover, a combination approach of ER with ablation therapies has promising results in selected patients, and may provide minimally invasive and effective treatment. This review mainly focuses on the role of ablative therapy in practice for squamous cell neoplasia of esophagus.