Dynamic changes of claudin 18.2 expression after systemic therapy in gastric and esophagogastric junction cancer

Claudin 18.2 (CLDN18.2) expression in advanced gastric/esophagogastric junction adenocarcinoma changes frequently during systemic therapy. In paired samples from 155 patients, positivity rose from 54 (34.84%) before treatment to 61 (39.35%) after (p < .001); overall, 131 patients (84.52%) showed altered expression. Conversion rates did not differ between chemotherapy alone and chemotherapy plus immunotherapy, supporting CLDN18.2 reassessment before targeted therapy.