A Prospective non-interventional study (NIS) of trastuzumab deRuxtecan (T-DXd) for adult patients with advanced HER2-pOsitive gaStric or gastroesoPhageal junction (GEJ) adEnocarcinoma who have Received a prIor Trastuzumab-based regimen, accompanied by a disease registrY of patients treated with conventional therapies in a real-world setting in Europe (PROSPERITY).