A Study to Evaluate Nivolumab in Patients With Unresectable Advanced/Metastatic Gastric Cancer and Gastroesophageal Junction Cancer

Inclusion Criteria: * Participants aged ≥ 18 years at date of first administration of nivolumab * Confirmed diagnosis of unresectable advanced or metastatic Gastric Cancer (GC) or Gastroesophageal Junction Cancer (GEJC) (histologically or cytologically) * Participants newly received nivolumab as first-line (1L) treatment between 15 June 2018 and 30 June 2023 * Participants with at least one tumor assessment after index date except for death or discontinuation due to Adverse Events Exclusion Criteria: * Participants with primary malignancies other than unresectable advanced or metastatic GC/GEJC * Participants who participate in an interventional clinical trial in or before 1L nivolumab treatment for advanced/metastatic GC/GEJC * Participants with known HER2 status positive * Participants who investigator deems inappropriate for inclusion, for example clinical data was incomplete