Impact of Autoimmune Gastritis on Occurrence of Metachronous Gastric Neoplasms after Endoscopic Resection for Gastric Neoplasms

SIMPLE SUMMARY: Autoimmune gastritis (AIG), characterized by antibody production against gastric parietal cells, is associated with a higher incidence of neuroendocrine tumors and gastric cancers. Metachronous gastric neoplasms become a major concern after endoscopic resection (ER) for early gastric cancer lesions. We assessed the impact of AIG on MGN following ER. The AIG group had higher MGN rates (45.0% vs. 18.3%), with similar patterns of metachronous tumors. Multivariate analysis revealed AIG (HR 3.32) was linked to MGN occurrence. Because AIG patients face a greater MGN risk post-ER, positive anti-parietal cell antibody test results necessitate vigilant monitoring and management for timely treatment. ABSTRACT: Gastric cancer is the fifth most common cancer and the third leading cause of cancer-related deaths worldwide. Autoimmune gastritis (AIG) is characterized by antibody production against the gastric parietal cells, reducing the number of functional parietal cells. It is also associated with an increased susceptibility to gastric neuroendocrine tumors and gastric cancer. Endoscopic resection (ER) is an effective treatment for early gastric cancer; however, metachronous gastric neoplasms (MGN) can develop. This study aimed to evaluate the clinical effect of AIG on the occurrence of MGN after ER for gastric neoplasms. We retrospectively analyzed patients who underwent ER for gastric neoplasms. Patients with multiple lesions, recurrent lesions, or a history of partial gastrectomy were excluded. The presence of AIG was determined using anti-parietal cell antibody (APCA) testing. Follow-up endoscopy and metachronous tumor occurrence rates were compared between the AIG and non-AIG groups. Of the 569 patients, 282 underwent APCA testing and 20 (7.1%) were diagnosed with AIG. The incidence of MGN was significantly higher in the AIG group than in the non-AIG group (45.0% vs. 18.3%); however, the MGN occurrence pattern was similar between the two groups. Multivariate analysis revealed that AIG (HR 3.32, 95% CI 1.55–7.10, p = 0.002) and a higher body mass index (HR 1.16, 95% CI 1.06–1.27, p = 0.002) were independent factors significantly associated with the occurrence of MGN. Patients with AIG have a higher risk of metachronous lesion occurrence after ER for gastric neoplasms. Positive results of APCA testing have independent clinical implications for predicting MGN. Proper monitoring and management are essential for early detection and treatment of recurrent lesions in patients with AIG.