AUTHOR=Sun Ya-hui , Ma Yan , Chen Liang , Li Hai-rong , Liang Xian-Wen , He Xiong-hui , Zou Ke-jian TITLE=Case Report: Pathological complete response achieved with neoadjuvant immunochemotherapy in synchronous multiple gastric adenocarcinoma JOURNAL=Frontiers in Immunology VOLUME=Volume 16 - 2025 YEAR=2025 URL=https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2025.1611281 DOI=10.3389/fimmu.2025.1611281 ISSN=1664-3224 ABSTRACT=Synchronous multiple gastric cancers (SMGC) represent a rare clinical entity with no established treatment guidelines. We report a 76-year-old female with two synchronous poorly differentiated adenocarcinomas (dMMR/MSI-H phenotype) in the gastric lesser curvature, clinically staged as cT4bN2M0. Following three cycles of neoadjuvant immunochemotherapy, the patient demonstrated remarkable tumor regression (RECIST 1.1 partial response) and subsequently underwent R0 distal gastrectomy. Histopathological examination confirmed a pathological complete response (ypT0N0, TRG 0).To our knowledge, this represents the first documented case of SMGC achieving pCR with neoadjuvant immunochemotherapy. Our findings suggest that PD-1 inhibition combined with chemotherapy may induce profound tumor regression in SMGC, even in cases with high tumor burden, potentially converting unresectable to resectable disease. This case provides compelling evidence for incorporating immunotherapy in SMGC management and warrants further investigation through clinical trials.