A prospective evaluation of high-magnification chromoscopic colonoscopy in predicting completeness of EMR

Background: EMR is used to treat flat and sessile lesions in the colon. The aim of this study was to prospectively assess the efficacy of high-magnification chromoscopic colonoscopy in predicting complete resection margins after EMR. Methods: A total of 1250 patients underwent colonoscopy by using a magnifying colonoscope. Chromoscopy with indigo carmine and crystal violet dye solutions was used to assess mucosal pit patterns. EMR was performed by using the saline solution inject-and-cut technique. After EMR, resection margins were inspected by using high magnification, and completeness of excision was predicted from the surface pit pattern. This was compared with completeness of excision as determined histopathologically. Results: A total of 684 lesions were treated by EMR (62 piecemeal) in 602 patients. The sensitivity of high-magnification chromoscopic colonoscopy for predicting remnant tissue in the lateral margins and the deep margins were, respectively, 79% and 80%. Specificity for both margins was 97%. The overall accuracy of high-magnification chromoscopic colonoscopy in predicting incomplete resection after EMR in the lateral axis and the deep axis was, respectively, 93% and 95%, where the true respective fractions of incomplete resections were 17% and 10%. Of the single en bloc EMRs performed, 77 (12%) had histopathologic evidence of incomplete resection in either axis, compared with 60 (97%) of the 62 piecemeal resections. Piecemeal resection was more likely to result in incomplete resection compared with en bloc EMR (p < 0.001). Complete resection by EMR was more likely if the lesion was sessile instead of flat (p < 0.001). Conclusions: High-magnification chromoscopic colonoscopy as an in vivo modality for prediction of remnant tissue after EMR has a high overall accuracy, but further studies assessing long-term outcome and cost-effectiveness compared with conventional colonoscopic techniques are required.