P-217 A retrospective, pathologist-based assessment of immunohistochemistry assay for CLDN18.2 expression in digestive system adenocarcinoma

Claudin 18 (CLDN18) represents an attractive drug target for gastric and pancreatic cancers. A more comprehensive understanding of CLDN18 expression is essential future implanting effective digestive system adenocarcinomas (DSAs) management. We conducted a retrospective immunohistochemistry evaluation in five DSAs (n = 834) using the anti-CLDN18 (clone 43-14A) antibody. Cases with immunochemistry staining signaling 2+–3+ intensity ≥75% tumor cells were defined as positive. observed higher positive rates (cut-off ≥75%) three DSAs: (GAD, 46.1%), (PAAD, 26.0%), gallbladder (GBAD, 12.4%); whereas CLDN18-positive cases rarely identified colorectal (COAD, 1.7%) intrahepatic cholangiocarcinoma (IHCC, 10.1%). In PAAD, high rate was determined patients well differentiation, no peripheral fat invasion, at early pTNM stage. GBAD, subgroups younger age (< 60 years old), or pT stage, pN GBAD showed significantly better overall survival (OS) disease-free (DFS) than low expression. Three types levels expression, GAD, may benefit most from therapies. The correlations clinicopathological characteristics prognosis suggest that stage could treatment can function pivotal regulative molecule GBAD.