Learning Effect of Diagnosing Depth of Invasion Using Non-Extension Sign in Early Gastric Cancer

Background: Determining the depth of invasion is important when considering therapeutic strategies for early gastric cancer (EGC). We determined the effects of learning the non-extension sign, that is, an index of T1b2 in EGC, on identifying its depth of invasion. Methods: Endoscopic images of 40 EGC cases (20 showing positive non-extension sign on endoscopy as T1b2 and 20 showing negative non-extension sign on endoscopy as T1a-T1b1) were randomly displayed on PowerPoint. Participants read endoscopy findings (pretest) and attended a 60-min lecture on how to read the non-extension sign. Then, they read the same images using the non-extension sign as the marker (posttest). The primary endpoint was a change in accuracy rate for determining the depth of invasion before and after attending the lecture, for nonexperts (< 80%). Results: Among 35 endoscopists, 12 were nonexperts; their test results were used for analyses. Accuracy rates for pretest and posttest among nonexperts were 75.2 and 82.5%, respectively, showing a significant increase in the accuracy rate after learning to read the non-extension sign (p = 0.003). Conclusion: Nonexperts' diagnostic ability to determine the depth of invasion of EGC improved by learning to read the non-extension sign. Thus, the non-extension sign is considered a simple and useful diagnostic marker.