Mo1761 RISK FACTORS OF ACCIDENTAL PIECEMEAL ENDOSCOPIC MUCOSAL RESECTION FOR COLORECTAL TUMORS 10 MM OR MORE IN DIAMETER

The majority of colorectal tumors 10mm or more are often resected by endoscopic mucosal resection (EMR). Due to the high incidence rate of local recurrence associated with piecemeal resection (EPMR), en bloc resection is desirable. However there are few reports on the risk factors of accidental EPMR. Thus the aim of this study was to examine risk factors of EPMR for colorectal tumors 10mm or more. There were 4441 colonic polyps treated with endoscopic resection between January 2007 to May 2018 in Chiba university hospital. Out of these polyps, 1069 tumors 10mm or more treated with EMR were selected. These tumors were divided into accidental EPMR group (Group A) and en bloc resection group (Group B). We compared patients’ character such as age, sex and tumors’ character such as morphology, location, size.Adverse event rate(post operative bleeding and perforation) were also compared. Furthermore risk factors of accidental EPMR was analyzed with multivariate as well as univariate analysis. Backgrounds of each group were as follows. Group A (94 patients, 135 tumors, mean age 67.9 ± 11.1, M:F =64:30); Group B (465 patients, 934 tumors, mean age 64.9 ± 11.9,M:F=298:167 ) There were no significant difference regarding those factors. Tumor size was significantly larger in Group A(mean tumor size (mm), 20.6 ± 11.0) than in Group B(mean tumor size (mm), 15.1±5.8)(p<0.05, unpaired t-test). There were no significant differences between the two groups as for the adverse events rate.In univariate analysis, the risk of accidental EPMR was significantly higher for tumors 30 mm and more. (Hazard ratio (HR) = 8.545; 95% confidence interval (CI) = 4.667-15.647; p <0.05). Protruded lesions have a low risk of accidental EPMR (HR = 0.285; 95% CI= 0.196-0.413; P<0.05), and cancers have a higher accidental EPMR risk (HR = 1.632; 95% CI= 1.123 -2.371; p<0.05).In multivariate analysis, tumor size 30mm and more was the most critical risk factor of accidental EPMR (HR= 7.582; 95% CI= 3.930-14.627; P<0.05). Tumor size of 30 mm or more was the risk factor of accidental EPMR. Also, we should pay attention to tumors that are not protruded and presence of cancer. To achieve en block resection, tumors 30mm and more should be treated with other endoscopic treatment such as endoscopic submucosal dissection.