The pocket-creation method may facilitate endoscopic submucosal dissection of large colorectal sessile tumors.

Resecting large colorectal sessile tumors using endoscopic submucosal dissection (ESD) is challenging because of severe submucosal fibrosis. Previously, we reported that ESD strategy using the pocket-creation method (PCM) is useful for large colorectal sessile tumors, but there are no large studies reporting the effectiveness and safety of the PCM for resection of large colorectal sessile tumors. This was a retrospective review of 90 large colorectal sessile tumors in 89 patients who underwent ESD in our institution. Large colorectal sessile tumors were defined as polypoid lesions 20 mm or more in diameter. We divided them into PCM (n = 40) and conventional method (CM) groups (n = 50). The primary outcome measure was en bloc resection. The inverse-probability-treatment weighting (IPTW) approach was used to adjust for selection bias. Both PCM and CM achieved high en bloc resection (100 % vs. 94 %, non-adjusted  = 0.25, IPTW-adjusted  = 0.19) and R0 resection rates (88 % vs. 78 %, non-adjusted  = 0.28, IPTW-adjusted  = 0.27). When PCM was used, the rate of pathologically negative vertical margins was significantly greater than with the CM (IPTW-adjusted  = 0.045). The dissection time was significantly shorter (IPTW-adjusted  = 0.025) and dissection speed faster (IPTW-adjusted  = 0.013) using the PCM than when the CM was used. There was no significant difference in the incidence of adverse events (intraprocedural perforation and delayed bleeding, IPTW-adjusted  = 0.68).  Although en bloc resection and R0 resection rates were similar, PCM significantly increased the rate of negative vertical margins with rapid dissection for treatment of large colorectal sessile tumors.