Observational Study of Patients Treated With Nivolumab and Chemotherapy for Advanced or Metastatic Esophageal, Gastroesophageal or Gastric Cancer in France

Inclusion Criteria: Cohorts 1 \& 2 * Adult participants (at least 18 years of age at time of treatment decision) * Participants treated with nivolumab in combination with fluoropyrimidine- and platinum-based chemotherapy (according to the French current marketing authorization) for the treatment of Gastric Adenocarcinoma, Gastro-Esophageal Junction (GEJ) adenocarcinoma, Esophageal Adenocarcinoma (EAC) or Esophageal Squamous Cell Carcinoma (ESCC) and prior to study participation. * Participants who provided oral informed consent to participate in the study Cohort 1 only • Diagnosis of untreated HER2 negative advanced or metastatic gastric adenocarcinoma, GEJ adenocarcinoma or EAC whose tumor express PD-L1 with a CPS ≥5 Cohort 2 only • Diagnosis of untreated unresectable advanced, recurrent or metastatic ESCC with tumor cell PD-L1 expression (TPS) ≥1% Exclusion Criteria: Cohorts 1 \& 2 * Participants with a primary diagnosis of a cancer other than advanced or metastatic gastric adenocarcinoma, GEJ adenocarcinoma, EAC or ESCC, within the past 5 years. * Participants currently enrolled in an interventional clinical trial for his/her advanced or metastatic gastric adenocarcinoma, GEJ adenocarcinoma, EAC or ESCC. * Pregnant women * Participants under guardianship