Real-World Observational Study to Describe Treatment Patterns in Patients With HER2-Positive Locally Advanced or Metastatic Gastric or Gastroesophageal Junction Cancer in East Asia

Inclusion Criteria: * Adult participants at the time of 1st LOT (Index Date 1e) initiation - Adult patients ≥18 years old. (Please follow local regulatory requirements if the legal age of consent for study participation is \>18 years old.) * Participants or next of kin/legal representatives who are willing to provide written informed consent as per the local regulations (if IRB/IEC/EC grants a permission to waive informed consent, it is not necessary). * Participants who were pathologically and/or clinically diagnosed with locally advanced or metastatic gastric or gastroesophageal adenocarcinoma (de novo advanced disease, relapsed/progressed) since January 1, 2016, and its record is available at the study participating site. * Participants whose HER2 status were pathologically confirmed HER2-positive (IHC3+ or IHC2+/ISH-positive) before/at the Index Date 2f based on the most recent archived tumor tissue sample to the Date of Diagnosisg, and its record is available at the study participating site. * Participants who received at least 1 LOT for HER2-positive locally advanced or mGC/GEJC in an advanced setting, and its record is available at study participating site. Trastuzumab or its biosimilar use is not required. °Progression on or within 6 months post neoadjuvant or adjuvant therapy is counted as "rapid progressor" in a neo-adjuvant/adjuvant setting, and thus equivalent to advanced/metastatic disease failing 1 LOT. * Participants who have at least 6 months of follow-up …