A Study of Treatment Patterns in HER2-positive Unresectable and Advanced Gastric/ Gastroesophageal Junction Cancer in China

Inclusion criteria * Patients with pathologically diagnosed locally advanced unresectable or metastatic GC/GEJC (limited to those diagnosed since October 1, 2017) and initiating first-line treatment between January 1, 2018, and March 31, 2023 * Patients aged ≥ 18 years at the time of diagnosis with locally advanced unresectable or metastatic GC/GEJC; HER2-positive status2, determined by either tissue samples from the first biopsy or liquid biopsy samples (if a patient has both tissue and liquid biopsy samples, tissue samples will be the standard). Exclusion criteria * Patients with other primary malignant tumors * Patients enrolled in clinical trials and receiving active anti-cancer therapy after July.1, 2017 (excluding retrospective studies). * Patients with critical missing data in medical records or otherwise deemed for inclusion by the investigator