Eradication of <b><i>Helicobacter pylori</i></b> Induces Immediate Regressive Changes in Early Gastric Adenocarcinomas

<b><i>Objective:</i></b> <i>Helicobacter pylori</i> eradication is expected to prevent gastric cancer. However, morphological alterations after eradication often hinder accurate diagnosis. Therefore, we evaluated endoscopic and histological changes in gastric tumors after eradication of <i>H. pylori</i> in a time-dependent manner. <b><i>Methods:</i></b> We classified 144 cases of endoscopic submucosal dissection (ESD) of early gastric cancer into the following categories: (i) patients positive for <i>H. pylori</i> with no eradication history<i>,</i> (ii) patients positive for <i>H. pylori</i> who underwent ESD 2 months after eradication, (iii) patients negative for <i>H. pylori</i> with an eradication history of at least 6 months before ESD, and (iv) patients negative for <i>H. pylori</i> with an unknown history. We compared endoscopic and histological factors between the groups. <b><i>Results:</i></b> The characteristics of cancers positive for <i>H. pylori</i> were exploding shape, superficial high-grade atypical epithelium, and a surface proliferating zone. <i>H. pylori</i> eradication induced a series of endoscopic and histological changes, including shape ­depression, appearance of surface regenerative and lower-grade atypical epithelium, and a downward shift of the proliferative zone within a period as short as 2 months. <b><i>Conclusion:</i></b> <i>H. pylori</i> eradication rapidly causes cancer regression and leads to tumor shrinkage, diminished atypism, and shortened proliferative zone, resulting in drastic morphological changes.