Trastuzumab Deruxtecan to Treat HER2 + Newly Diagnosed Metastatic GI Cancers

Purpose: This clinical trial is designed to evaluate the safety and effectiveness of Trastuzumab Deruxtecan for patients with HER2 Positive Newly Diagnosed Metastatic Esophageal, Gastric, GEJ Cancer. The goal is to determine how well this treatment works and to identify any potential side effects. Who Can Participate: We are looking for Participants with histologically confirmed HER2 positive locally advanced unresectable and/or metastatic esophageal, gastric or GEJ adenocarcinoma with an ECOG PS of 2 and measurable disease according to RECIST 1.1 within 42 days prior to registration. Participants will be carefully screened to ensure they meet the study requirements. What to Expect: Participants will undergo 6.4mg/kg, IV infusion of Trastuzumab deruxtucan over the course of the study. They will receive detailed information about the study and will have the opportunity to ask questions before deciding to participate. Informed consent will be obtained to ensure that participants understand the study's purpose, procedures, risks, and benefits. Safety Monitoring: The health and safety of participants are our top priority. An Independent Data and Safety Monitoring Committee (DSMC) will regularly review the study data to ensure participant safety and to monitor for any adverse events. Any serious side effects will be reported and addressed promptly. Benefits and Risks: While the study aims to provide potential benefits, such as improved treatment options for HER2 Positive Newly Diagnosed Metastatic Esophageal, Gastric, GEJ Cancer there may also be risks involved. Participants will be informed of all possible risks before enrolling in the study. Confidentiality: All personal information will be kept confidential, and data will be used only for research purposes. Contact Information: For more information about this study, please contact PhaseIICRA@medicine.bsd.uchicago.edu