SELF-LIMITING RISK OF METACHRONOUS GASTRIC CANCERS AFTER ENDOSCOPIC RESECTION

Background: Since endoscopic resection (ER) has been established as a treatment for early gastric cancer, metachronous multiple cancers have become a problem. It is unclear whether the risk of metachronous cancer is self-limiting or permanent. The aim of this study was to evaluate the incidence of multiple cancers after ER during a long-term follow-up study. Patients and Methods: A total of 234 patients who received initial ER for early gastric cancers were evaluated retrospectively. ER included endoscopic mucosal resection and endoscopic submucosal dissection. Patients were followed up with endoscopy for 3.0-19.6 years (median, 5.0 years), including 40 patients surveyed for more than 10 years. Accessory cancers detected after ER, but which could be retrospectively viewed in pre-ER pictures, were evaluated in the metachronous group. Results: Thirty patients (12.8%) developed 36 metachronous multiple cancers. The median interval between the discovery of metachronous cancer and the initial ER was 3.2 years; the longest interval was 9.7 years. Eight (22.2%) of the 36 metachronous cancers could be detected retrospectively in the picture record from pre-ER. The Kaplan-Meier curve of cumulative incidence of metachronous cancers stopped increasing after 10 years of follow up. Conclusions: Although the residual gastric mucosa after ER is thought to be a high-risk environment, the high risk may only be the result of occult synchronous cancers. It is probable that the high risk of metachronous cancers is not continuous after 10 years.