A Study in Greece Observing How Patients With Stomach and Esophageal Cancer Are Diagnosed and Treated in Everyday Medical Practice

Inclusion Criteria: * Patients aged ≥18 years upon gastric/GEJ adenocarcinoma diagnosis. * Written signed and dated informed consent by the patient (or their legally acceptable representative, as applicable). For deceased patients on the date of study entry a waiver of consent must be approved by the Hospital EC/IRB. * Patients diagnosed with histologically confirmed, stage II to IVB adenocarcinoma of gastric/GEJ, between June 1st, 2025 and the end of the recruitment period (Q3 2027). Exclusion Criteria: * Patients who participate or participated during the data collection period (prospective and retrospective) in any clinical investigation/clinical trial that includes interventions that fall outside the everyday clinical practice. * Patients who have participated in the design and/or the conduct of the study. * Patients with another primary malignancy within the last 5 years, for which systemic anticancer treatment is required after the diagnosis of gastric/GEJ cancer.