A Study of Trastuzumab DeRuxtecan for Patients With Advanced HER2-pOsitive GaStric or GastroesoPhageal Junction AdEnocarcinoma Who Have Received a PrIor Trastuzumab-based Regimen Accompanied by a Disease RegistrY of Patients Treated With Conventional Therapies (PROSPERITY)

Inclusion Criteria: * Male or female adult patient (age ≥ 18 years) with HER2 + advanced gastric or GEJ adenocarcinoma who have received a prior trastuzumab based regimen * Histological or cytological confirmed diagnosis of advanced HER2 positive gastric cancer or GEJ * Documented HER2 + status (archival sample or recent sample prior 2L therapy) * Decision to newly initiate monotherapy T-DXd or conventional therapies per SMPC according to the physician's choice * Written dated and signed Informed Consent (ICF) to participate in the study Exclusion Criteria: * Patients who at time of data collection for this study are participating in or have participated in an interventional study that remains blinded * Pregnancy or breastfeeding No specific exclusion criteria are defined, as patients will be treated according to the proposed indication statements in the SmPC.