Tu1491 Correlation Between Adenoma Detection Rate (ADR) in Screening Sigmoidoscopy and Screening Colonoscopy

Abstract

colorectal cancers. According to the current Japanese guideline, additional surgical colectomy with lymph node (LN) dissection should be considered after endoscopic treatment even for cases where the depth of SM invasion is 1000mm or more. However, many patients who underwent additional colectomy didn’t have LN metastasis. This over-surgery problem has become a major issue. Aims: The aim is to investigate whether the depth of SM invasion is an appropriate risk factor for the LN metastasis in SM-invasive colorectal carcinomas. Methods: A total of 20072 colorectal neoplasms excluding advanced cancers have been resected endoscopically or surgically at our unit from April 2001 to May 2013. Of these, 853 SM-invasive cancers were included. Initial or additional surgical colectomy with LN dissection was performed in 567 cases, and of which LN metastasis was found in 52 cases (9.2%). There are two ways to measure the depth of SM invasion. One is to directly measure the vertical distance from the line of muscularis mucosae. The other is, when the line of muscularis mucosae is not easily identified due to cancer invasion, the surface layer of the lesion is used as a baseline. According to this rule, a pathologist in our unit categorized 816 lesions and measured their depth of SM invasion. Then, we analyzed the correlations between the depth of SM invasion and the other pathological factors including LN metastasis. Results: Of 567 lesions, 54 lesions (9.5%) were invaded SM!1000mm and 513 lesions (90.5%) showed SM S1000mm. The average SM depth of the lesions without LN metastasis was 3275.7 2441.4mm and that of the lesions with LN metastasis was 4307.4 2307.0mm. LN metastasis was found in 4 (7.5%) out of 53 lesions with SM! 1000mm and in 48 cases (9.6%) out of 502 lesions with SM S1000mm (pZ0.63). Of these 567 lesions, on the other hand, the muscularis mucosa could be identified in 180 lesions (31.7%). For the other 387 lesions (68.3%), the muscularis mucosa was recognized broken or disappeared respectively and the depth of SM invasion was measured from the surface layer. All the results turned out to be S1000mm. Once the muscularis mucosae was judged to be unclear and the surface layer was applied as the baseline, all the cases would be considered S1000mm. Conclusion: Although SM cancers with LN metastasis invaded actually deeper than the lesions without nodal metastasis, the depth of SM invasion was not a statistically significant risk factor for LN metastasis. How to measure the depth of SM invasion depend strongly on the judgement whether the muscularis mucosa could be identified or not. The reconsideration should be needed concerning the depth of SM invasion.