Colorectal EMR for nonpolypoid neoplasia achieves better outcomes when performed by expert endoscopists. The time point at which the endoscopist achieves expert level remains to be defined. The objective of this study was to establish a learning curve of colorectal EMR for nonpolypoid neoplasia based on residual tissue on surveillance colonoscopy and adverse event rate.

Five hundred seventy-eight consecutive patients underwent EMR of colorectal neoplasia by 1 of 3 primary endoscopists between December 2004 and September 2013 in a tertiary academic center. Primary analyses focused on the largest lesion for patients with more than 1 lesion (median age, 69 years; median polyp size, 30 mm; 51% en bloc resection). Data on surveillance colonoscopy were available for 74%. Learning curves were calculated for each of the 3 main outcome measurements: the presence of residual neoplasia on surveillance colonoscopy, endoscopic assessment of incomplete EMR, and the occurrence of an immediate bleeding adverse event.

Residual neoplasia on surveillance colonoscopy was present for 23.2% of patients, the rate of endoscopist-assessed incomplete EMR was 27.6%, and immediate bleeding adverse events occurred in 6.9% of patients. Although there was between-endoscopist variability, the overall rates of residual neoplasia and incomplete EMR decreased to below 20% to 25% after 100 EMRs; initial decreases in both rates were observed for earlier EMRs. Immediate bleeding adverse events occurred at a low frequency for each endoscopist across all EMRs. Perforation requiring surgical intervention occurred in 1 patient (0.2%).

This study demonstrated that an unexpectedly high number of 100 colorectal EMR procedures for large nonpolypoid colorectal neoplasia are required to achieve a plateau phase for crucial outcomes.