Hey, this is Doug Rex from Indiana University. I want to welcome you to a new series of colonoscopy tips called the ASGE SUTAB tip of the week. What's the most important development in endoscopic mucosal resection in the past decade? Arguably, it's the demonstration that after complete resection, thermal injury to the margin of the EMR defect dramatically lowers the recurrence rate at follow-up. The paradigm of modern inject and resect EMR-employing electrocautery is to remove all visible polyp tissue by snaring, or in the case of flat or fibrotic tissue, by avulsion and never to ablate visible tissue. Once all resection has been completed, the margin is treated thermally by STSC, ST for snare tip, using SC, soft coagulation current. Question, if the recurrence rate after piecemeal EMR is about 20%, how far does the effective application of STSC to the margin reduce that recurrence rate? Is it to 16, 13, 10, 5, or 2%? Brooker and colleagues at St. Mark's London tested the principle of thermal injury to the EMR margin in 2002. In a randomized trial testing APC, they showed a dramatic reduction in recurrence rate, but because the number of patients was low at 21 and the recurrence rate in controls was high at 64%, the result was not widely accepted. In 2019, Michael Burke's Australian consortium testing STSC in a randomized trial showed a dramatic reduction in recurrence from 21% to 5.2%. At DDW Virtual 2020, in an uncontrolled study of STSC, the recurrence rate was only 2.1%. Thus, thermal treatment of the margin after piecemeal EMR reduces the recurrence rate to a level equivalent to that seen after ESD and effectively eliminates recurrences as a rationale for ESD over piecemeal EMR. Before applying STSC, it's critical to systematically inspect the entire margin and remove all visible bits of polyp with snare or avulsion. Our target for STSC thermal injury will be the normal tissue exactly at the margin of the EMR defect and depicted here by the yellow line and arrows. As we apply the STSC to that precise margin, we'll see a zone of white thermal injury several millimeters wide develop and spread into the normal mucosa surrounding the EMR defect. Once we've completely removed the polyp by snaring and the use of avulsion if needed for flat or fibrotic portions, then and only then will we apply the snare tip thermal treatment to the margin. To do this, we must switch from the higher voltage forced coagulation current to the low voltage soft coagulation current to ensure safety. To perform STSC, we're going to switch the coag current from forced to soft. Soft coagulation current, effect four or five, max watts 80. Now we're ready to go. So the lesson of these studies is that recurrences come in from the margin and they may be starting from viable polyp tissue that is too small to be visible to the naked eye through the scope. If we can destroy that margin right on the margin aggressively around the entire circumference, we can dramatically reduce the recurrence rate. So you see how we're targeting exactly that margin, just that junction, doing it safely because we're on snare tip soft coag. As we apply the treatment, we expect to see this several millimeter wide white charred appearance develop on the mucosa adjacent to the EMR defect. And we want to check the entire 360 degrees to make sure there are no gaps in the treatment. Let's look at the real time treatment of the entire circumference of an EMR defect in the right colon using STSC. So we've switched from forced coag, the current that we typically use for snaring polyps. Because we're using the tip of the snare, we've switched over to the lower voltage soft coagulation current. And that's very important. I'm aware anecdotally of colleagues telling me that when they've used the snare tip on forced coag for one purpose or another, they've actually perforated the colon. So switching over to STSC, the low voltage current gives us a margin of safety, allows us to be quite aggressive in burning up that edge. Now you'll notice that we've got the snare tip out just a few millimeters. When we're moving transversely across the colon, I typically have maybe three, four millimeters of snare tip out there. Once we start moving down the longitudinal axis of the colon along that side of the EMR, you can put the snare tip out a bit further. You can move a little bit more quickly down that longitudinal axis. But stay focused right on that margin. Use torque of the scope, bend down as needed to get into all the nooks and crannies to make sure that you get a completely circumferential treatment. You don't leave any, even a millimeter or two of the margin untreated. When we're done, we're going to see this white char of that mucosa on the edge around the entire circumference. The current indication for STSC margin treatment is any colorectal lesion removed by piecemeal inject and resect EMR that employs electrocautery. But perhaps any piecemeal resection that employs electrocautery should be followed by STSC of the margin. Next week, when to perform clip closure of non-penunculated lesions on the ASGE SUTAB tip of the week.

colonoscopy tips

thermal injury

endoscopic mucosal resection

STSC

margin inspection