S1540: Laterally Spreading Tumors (LST) of the Colon: What Is the Role of Endoscopic Mucosal Resection (EMR) in the Endoscopic Submucosal Dissection (ESD) Era?

Abstracts S1539 Re-Interpretation of Hyperplastic Polyps Into Serrated Polyps: “Saw Toothed Lesions With Teeth” Veronika Karasek, Deepa K. Shah, Bo Wang, Francisco C. Ramirez Risk of colorectal cancer can be significantly diminished if all precursor lesions are removed via endoscopic polypectomy. Cancers will develop due to missed lesions on previous endoscopy, rapid cancer growth, flat lesions, and inappropriate recognition of their precursor lesions in endoscopy. The “hyperplastic polyp” is considered a benign lesion, whereas the “serrated adenoma” is a precursor to adenocarcinoma. The morphologic complexity of the serrated polyp is difficult to distinguish. Sessile serrated adenoma is primarily in the proximal colon with size ⱖ 10 mm and accounts for 17.5% of all proximal colon malignancies.Aim: To determine the number of small (6-9 mm) serrated colon polyps that may have been misclassified as hyperplastic polyps.Methods: All patients diagnosed with hyperplastic polyps in 2000, 2001 and 2005 were reviewed from an endoscopic database. Data collected: polyp size, location, mode of removal, characteristic shape, and presence of associated lesions. Hyperplastic polyps ⱖ 6-9 mm were re-evaluated by a GI specialized pathologist to determine if any of these hyperplastic polyps were actually serrated polyps.Results: 1382 patients had a histologic diagnosis of hyperplastic polyp in the study period. Of these, 118 had hyperplastic polyps 6-9 mm of which 104 (7.5%) pathology slides were found and re-evaluated. Of these 104 patients 81(78%) were reclassified as serrated polyps: 10(9.6%) as sessile serrated adenomas, 51 (49%) as traditional serrated adenomas, and 20 (19.2%) as serrated polyps (difficult to distinguish between the serrated polyp category). Of the reclassified polyps, 24(29.6%) were proximal and 57(70.4%) were distal. 21% were pedunculated and 31% had associated lesions as true adenomas or cancer. Only 1 cancer (in the rectum) was associated with an 8 mm serrated polyp in the transverse colon.Conclusion: In our series, 78% of ⱖ6-9 mm “hyperplastic” polyps were reclassified as serrated polyps demonstrating a much greater percentage than found in the literature. In contrast to the belief that serrated polyps usually occur in the right colon, we found them predominantly in the left colon with the exception of sessile serrated adenomas of which 70% were found proximally. Increased awareness of serrated polyps is necessary and a shorter surveillance interval for these premalignant lesions may need to be established. Reclassified “Hyperplastic Polyps” Serrated Polyp Serrated Adenoma Sessile Serrated Adenoma Totals

Proximal

Distal

Total

2 14 8 24

18 37 2 57

20 51 10 81

FU.All were treated with APC since desmoplastic reaction after EMR did not afford further submucosal injections. Nevertheless, none of these patients had disease recurrence at the EMR site at 18-month FU.CONCLUSION:EMR is a safe and effective treatment for most colorectal G-LST. However, ESD should be preferred for both G-LST greater than 60mm in length or 30mm in width and NG-LST since the failure rate of EMR is unacceptably high in these selected cases.

S1541 Accuracy of Probe Based Confocal Laser Endomicroscopy (pCLE) in Predicting Recurrence of Colorectal Neoplasia After Endoscopic Mucosal Resection Anna M. Buchner, Muhammad W. Shahid, Evelien Dekker, Victoria Gomez, Paul Fockens Background/Aims: Residual neoplasia after EMR of colorectal lesions is common. In previous studies, our group found 23% of EMR sites had residual neoplasia upon re-look endoscopy (Bacani JC et al, Surgical Endoscopy 2008). There is a critical need for imaging methods to accurately diagnosis residual disease, and guide re-treatment in real-time, without delay of biopsy. The pCLE allows imaging of colonic epithelium in vivo during colonoscopy and can be used for this purpose. The aim of our study was to estimate accuracy of pCLE for detection of residual neoplastic tissue at site of prior EMR with histopathology as gold standard. Methods: The sites of prior EMR were assessed during endoscopic inspection within 6 months of initial EMR using pCLE system (Mauna Kea Tech). Confocal video sequences of EMR scar were stored and reviewed off-line blinded to histopathology and endoscopic appearance. Tissue confirmation by biopsies or polypectomy/re-EMR was performed in all cases. Results: 65 patients from two medical centers (MCF, AMC) completed follow up colonoscopies for the evaluation of their EMR sites. Residual neoplasia was confirmed by histology in 11 cases which was detected by pCLE as well. The estimates of sensitivity, specificity, accuracy, PPV and NPV with the 95% CI are listed in Table 1. A high false positive rate (inverse of PPV) was seen with pCLE (54%) and NBI (65%) which could lead to overtreatment if used in instead of biopsy confirmation and repeat colonoscopy. There was a trend toward superiority of pCLE compared to NBI (p value⫽0.077).Conclusion: The pCLE imaging may be helpful in detection of recurrence of neoplasia at prior EMR site and in directing its removal/ablation at time of follow up colonoscopy. Compared to the two other alternative strategies for EMR follow up: 1. biopsy and empirically retreat all, or 2. biopsy and repeat colonoscopy for positive results: pCLE can either reduce almost half of over treated cases or avoid repeat colonoscopy-treatment in almost one fifth of cases with residual disease. Table 1

S1540 Laterally Spreading Tumors (LST) of the Colon: What Is the Role of Endoscopic Mucosal Resection (EMR) in the Endoscopic Submucosal Dissection (ESD) Era? Marco Gentile, Fulvio Spirito, Rosario Forlano, Vito Annese, Angelo Andriulli, Francesco Perri BACKGROUND:EMR is performed by Western endoscopists to treat LST of the colon. However, for lesions larger than 25mm, EMR is limited by its inability to achieve en-bloc resection. For this reason, Japanese endoscopists advocate the use of ESD for LST of the colon greater than 25-30mm. However, the technical difficulty of ESD is high as well as its complication rate.AIM:To assess both safety and efficacy of EMR in achieving radical resection of colorectal LST, and to examine the main features that make ESD preferable.METHODS:All patients referred to our Institution for colorectal LST were prospectively enrolled during a 1-year period (Jan-Dec 2007). After EMR was performed, all patients underwent endoscopic follow-up at 1, 3, 6, 12, and 18 months after the procedure. Inject and cut technique was used with 1:100,000 epinephrine diluted with methylene blue(0.2%). Indian ink tattoo was done to locate the site of the resected lesion.RESULTS:In the study period, 4,856 patients underwent colonoscopy and 273(5.7%) flat lesions were identified. Of them, 144(3%) met the Paris criteria for LST, with a mean size of 44 mm(range:10-130 mm). 110(76.4%) Granular typeLST(mean size: 38 mm; range 10-58 mm) were removed en bloc, and histology revealed 1 Ca with submucosal invasion, 24 Ca in situ, 85 adenomas(32 with HGD).30(20.8%) G type-LST were removed with piecemeal resection because of their size(⬎60 mm in length or ⬎30 mm in width).4(2.8%) Non-Granular type LST had a central smooth surface and after submucosal injection no lift sign was seen. After an unsuccessful attempt of dissection, they were referred to surgery with surgical specimens displaying adenocarcinoma with submucosal invasion in all cases. None of the patients developed major complications (death or perforation) during EMR. In 23(16%) patients, early or delayed bleeding occurred after EMR but complete haemostasis was achieved endoscopically.A complete resection without disease on the edge of the lesions was achieved in 102(92%) patients of the en bloc removal group and in 15(50%) of those of the piecemeal resection.In the remaining 23 patients(8en-bloc removal and 15 piecemeal resection)residual adenomatous tissue was found at the EMR site at 1-month

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Prevalence Sensitivity Specificity Positive Predictive Value Negative Predictive Value Accuracy

pCLE

95% CI

NBI

95% CI

17% 100% 74.1% 44% 100% 78.5%

(9.2-28.7) (67.9-100) (60.1-84.6) (25.0-64.7) (89.7-100)

17% 63.6% 75.9% 35% 91.1% 73.9%

(9.2-28.7) (31.6-87.6) (60.7-84.9) (16.3-59.1) (77.9-97.1)

S1542 Magnetic Resonance Colonography for Colorectal Cancer Screening in Hereditary Non-Polyposis Colorectal Cancer Gene Mutation Carriers Eu Jin Lim, Finlay A. Macrae, Christopher Leung, Alex Pitman, Damien Stella, Gregor J. Brown Carriers of mismatch repair gene mutations have a 50-80% risk of colorectal cancer (CRC). Current guidelines recommend 1-2 yearly colonoscopy, with risks of bowel perforation and over-sedation, for CRC screening. We evaluated magnetic resonance colonography (MRC) to determine its suitability as a non-invasive alternative to colonoscopy (CC) for CRC screening in this high-risk population.In a pilot study, adult mismatch repair gene mutation carriers had both screening procedures done on the same day after standard bowel preparation. MRC was performed on a 1.5 Tesla MRI machine with water enema and scopolamine for bowel distension, followed by CC. Experienced MRI radiologists read the scans and rated the image quality. An endoscopist unaware of MRC findings performed CC, with the MRC results released after completion of CC. If lesions were detected with either technique, their number, size and location within the bowel were noted. Extra-colonic pathology on MRC was also recorded. Post-procedure, patients compared discomfort and inconvenience of MRC and CC on a visual analogue scale.30 patients (mean age 47 years, 43% male) were recruited from 2005 to 2009. 33% had previous polyps and 7% had previous CRC. 83% of the MRC scans were of adequate to good quality as read by 2 radiologists independently. MRC detected 3 lesions in 3 patients (size 70, 36, 17mm) - 2

Volume 71, No. 5 : 2010 GASTROINTESTINAL ENDOSCOPY AB189